Honestly, I would check electronics retailers (Mauser, Digikey, etc.) first.
Open-Frame would not be ideal, I agree.
A quick search bought up three supplies (neither is cheap):
Meanwell GST220A36 would set you back $82
ETA-USA MTE200-36SX $143
TDK-Lambda TDM250PW360D $210
Looking at prices, I would try the amazon find you did earlier.