I think we've already fallen into the weeds in another diy darkroom sink thread regarding what will last, what will not and general feasibility of the diy route.
financial budget, time availability and diy skills. You need to figure out how these 3 things directly affect you.
I would suspect that being in the DC area, there should be some architectural salvage, some restaurant equipment supply places, and a lively secondary market (craigslist, fb marketplace, etc) I would scan/ look at those sources and see if anything works, then figure out time/cost to acquire the used items and whether further modifications needed render the used/salvage item make any sense.
There are a ton of nicely built diy sinks in these forums, short of the "right" thing popping up for free, I would definitely build my own but I am a carpenter by trade which irons out some of the kinks for a person that may/may not own all of the tools I have available to me.
If you go down the plywood route, at least upgrade to something with an "A" face. it will be much easier to finish regardless of your finish choice (but it will cost more).