Welcome! You have a good 6502 history and setup there... I can't help directly with choice of dual port RAM, but searching the forum I see the Romulus project used an IDT7007 32K x 8 Dual-Port RAM.
I generally search Farnell or Digikey for components - it gives an idea of availability and price even if you buy from elsewhere. It's quick to select, for example, through hole or 5V parts if that's what you want.
Example, Digikey has 3446 matches for dual port RAM.
http://www.digikey.co.uk/products/en/in ... ort%20sramJust 1807 are 5V supply. Just 48 are current instock parts. Just 2 of those are through-hole, namely the IDT 7130 and 7132, which is to say 1k x 8 and 2k x 8.
(As we've noted many times, 5V and through-hole is becoming ever more niche, so we're pushed towards surface mount and/or 3V supply)
I see you've already found on ebay
IDT7005L55J HIGH-SPEED 8K x 8 DUAL-PORT STATIC RAM (in LCC package, 5V)
CY7C006-35JC CYPRESS 16K x 8/9 Dual-Port Static RAM (in PLCC, 5V)
So, these may not be new, and they are surface-mount, but that might be fine for your purposes.
You'd be well-advised to read the datasheets, and of course to check the reputation of the supplier.