You can get a 6-volt SLA battery for a lot less than $100.

Any device to do what you propose, at an amperage suitable to operate a car starter, is going to cost you a lot more.

Go buy a battery.

You might check local auto parts stores and service stations to see if they have a used battery that cn be charged up for one last use.

Phark is right, You want a real 6V car battery and it shouldn't run $100. I see them for online in the $60 range. See if there's a Batteries Plus near you.

NAPA still sells a battery intended for early 6-volt VW Beetles. I don't know the price, but the part number is BAT 5019L.

Another option, if you have the room, would be a 6 volt golf car battery. See the chart referenced below for dimensions. It's at the bottom (type GC2).

Golf car batteries are commodity items. You can usually buy one at Sam's Club for around $70-75. Or ask around at your local golf course; I've bought entirely serviceable used ones for less than $20.

Here is a link that might be useful: Battery dimensions by BCI group

You don't. If you are just going to start it put in a 12 volt battery and don't turn on anything that requiers 6 volts. The 6 volt starter will last a LONG time on 12 volts.

No, it's not likely to hurt the starter; but if you do as Kalining suggests, don't run the engine for too long. The points and coil may not like the higher primary voltage and current. (That's why 12 volt point-ignition cars had ballast resistors - to limit primary current.)

As I suggested above, the easiest and safest answer is to find a decent used golf car battery. They're really robust. Many years ago, I used to jumpstart my neighbors' cars from my golf car (using 2 of the batteries) on subzero mornings. It worked at least as well as the wreckers' rigs, and a lot better than jumping from a running car. (Jumping the battery, I mean.)

I hate it when you guys don't just answer the question... This isn't just for him you know... And if he has any junkers laying around in pretty sure the resistor block for a blower motor in a Chevy truck size vehicle would work but not all vehicles will have one that big.... Thanx guys, I have a question too but I won't even bother

Oh yeah I suppose I should have specified the resistors for everything except for the starter sorry to confuse you guys

Well, you come here with no info and you hurl insults, and you expect to be taken seriously.

A resistor block will work fine for a fixed load, but it will not solve the general problem. The voltage will go up and down with the load. Using a 12V for the starter was discussed NINE YEARS AGO. A DC-to-DC converter for things other than the starter, will run just about $100 which you'd have to go through about 4 batteries to make back your investment in the materials (not even counting the labor).