Is it UL listed?

Or ANY testing lab?

If it does not have a listing the price is an absolute rip off.

It looks like it's a cord, a box, a couple of 20A circuit breakers and a couple of receptacles. The hardest part of making one would be the metal work for the enclosure.

If you really have an unused dryer outlet, why not just change the breaker to a single pole 20A, cap the red wire on both ends (won't be used), and replace the dryer receptacle with a normal 120V/20A receptacle. It certainly would be less expensive than this solution.

I don't have easy access to the breaker box to change it that way...I'm in a loft in NYC and changing the whole thing would require the landlord and an electrician...etc etc. I just want to be able to access the power as I don't have many outlets in my place.

I've done a little more research and now I'm not sure it's a dryer outlet. It has a three prong dryer receptacle but the old tenants used it to run a ceramic kiln. They mentioned it was 3-phase power. It's connected to a double pole 40amp breaker.

Is there any chance of purchasing or making some setup like the link I listed to allow me use of this outlet without changing the whole thing from the breaker to the outlet?

"They mentioned it was 3-phase power." What do they know?
Since this may or may not be true, the FIRST thing to do is determine what is there at present.
Go to the link and identify the receptacle that is in your apartment.

Here is a link that might be useful: Configurations

If it has a double pole breaker, it's not three-phase.

OTOH what are we doing about the lack of a neutral conductor which absent in normal 240v - 3 wire circuits?

There is no such thing as a "dryer outlet" or a "kiln outlet". There are outlets that are normally used for kilns or dryers and certainly you can use a kiln of some sort on an outlet that is used for a dryer.

Right now, identify the outlet on that nifty chart that bus driver linked. If you can look at your panel tell us if there are three main breakers or two?

Alrighty. Here's some more info. If I can I will try to post pictures when I get home later. In the breaker box for my unit there is a 40amp 2pole breaker which powers this specific outlet only. 3 6 guage wires run from the breaker box to an industrial safety switch just above the outlet. The outlet is currently fitted with a nema 10-30 receptacle that the previous tenants told me they switched out so a dryer could be attached. One red wire is connected to the Right pole, one red wire is connected to the Left pole, and one red wire wrapped in white electrical tape is connected to the middle pole. Prior to that the outlet was fitted with a nema 6-50 receptacle (which I still have) and powered a large ceramic kiln. I have never used this outlet for anything.

Based on your description, you don't have a ground in this 240/120V single phase circuit. If you're still inclined to re-purpose this circuit, I'd at least make sure that the receptacles are GFI protected. I'm not sure where (or if) you can buy such a device.

What you're looking for is called a "portable power distribution box" or a "spider box." Google will turn up a bunch of them, but you may have a hard time finding one that will plug into an old style 3-wire dryer receptacle.

Are there portable generator adaptors that will work safely?

Is this in metallic conduit? If so, that is your ground.
Turn off the power, install a 2 or 4 breaker box with 20 amp breakers after the safety switch to replace the 'dryer' outlet, install some receptacles and you are done.

Thanks for the info everyone. I think the 2 to 4 breaker box is the way to go. The wires are running in metal conduit. It's actually installed along the ceiling and wouldn't be too hard to run new wires from the breaker box...but if I don't have to I'd rather not. I'm assuming with the 40amp double pole breaker that powers the current outlet I can install two 20 amp single pole breakers in the box which will power two separate receptacles...

"Is this in metallic conduit? If so, that is your ground. "

Maybe.

If the plug is 3-prong there may not be an adequate ground available, even with metallic conduit.

3-wire dryer and rage circuits where a safety compromise from the start.

Many of the loads had 120 V portions (the drum motor in dryers, and the stove top elements in ranges) and shared the neural-ground.

The large size of the conductors typically made for very small voltage drops, so the device chassis did not have a very significant voltage present even at full 120 V loading.

Since this is a rented premises, the only thing to do is to use a unit that plugs in. Do not change anything about the wiring of the building. When the tenancy ends, unplug the unit and leave.
A competent electrician can make up the unit you need.