Remnants! Go to some fabricators and bargain, bargain bargain!

For the sink base, you might consider Barker Cabinets. You can have the cabinets built to whatever height/depth you spec...reasonably priced and great quality too!

No answer here, but I'll join your thread for ideas if I may.

My laundry will be installed in my kitchen (reno starting in July) and that's one of the last, unanswered questions. We thought we'd be able to have them under a full run of counter at regular height/depth, but because our walls are masonry and the water/drain/electrical etc. is all surface mounted. Therefore, they'll be at 30" deep.

My big fear is that, in my old house, I want quick and easy access to the drain area. So was initially thinking of something light (laminate?) that would lift off. But at 54x30, that still would be unwieldy. My current thought is that, whatever I do, have it go back to the back of the appliances, then have smaller 'panels' that can be lifted out individually above each of the appliances. I was thinking of having a cabinet maker make something to match my cabinets (natural cherry) or going with butcher block. I still may do one of those. But my granite fabricator reminded me that I'll have lots of granite left over, so I'd just be paying for fabrication if I had him make that. So we'll see where we're at after templating.

For the counter you (or contractor) could have a woodworker make up a self edged laminate counter....in Boston they can be had for approx $35LF at anywhere from 25-28" deep

We where able to cut down a large stainless steel counter from the kitchen when we remodeled to reuse. It has a integrated sink and works great in our laundry room. Maybe you can have a stainless steel counter fabricated to any depth you need and raise the 36 inch base cabinet with 2 x 4's to the desired height. Or just stagger the counter tops like the laundry rooms in the post below.

post on laundry room design:
https://www.houzz.com/magazine/contractor-tips-advice-for-laundry-room-design-stsetivw-vs~2710545-Tips--Wise-Advice-for-Laundry-Room-Design

How tall are you? Make sure that reaching across and into a sink with the top at 40-44" (don't forget the counter material or any underlay) will be comfortable. Don't use 2x4s if you want to go that high. Have your contractor install the base on top or 2x6s, and if he can plan ahead, he can frame that to house a toe kick drawer since you will have plenty of space for it.

My laundry is in a custom cabinet in my kitchen - I had it recessed so I ended up with a 24" bar height counter and used my same granite.

The back wall is actually the stairwell going down to the cellar so I had two access hatches cut - one so I could get to the water shut off and the other for gas shutoff / dryer vent.

I also installed a water sensor that will automatically shut off the water in the event of a flood / water issue as I couldn't figure out a way to plumb a permanent drain / pan and still be able to pull the machine in/out for maintenance or eventual replacement.

What about looking at IKEA desk tops rather than counters? There is a Linnmon desk top that is 59 X 29.5. I'm sure there are other options there too.

Here is a link that might be useful: IKEA Linnmon table top