So I'm one of those avid arcade machine collectors and have tons of interest and respect for the 6502 (and Z80 and 68000's).
A long time ago I received the inventory of a startup 80's arcade company.
Getting to the point: sitting in my attic are literally *thousands* of 40 pin sockets (from the 80's!). If any active contributors here need of some (for your personal use - not selling), drop me a message. Happy to send up to 50 to anyone that needs some for their 6502 projects. Would imagine it'd be fair to ask for actual shipping costs - otherwise they're free.
These are from a company called Entertainment Sciences (you may not have heard of them). They were developing a machine called 'Bouncer' which some consider the arcade collector 'holy grail'. They also had a low-release game called Turbo Sub.
Sockets are open but the pins aren't straight down, they have a midway bend-out of a few degrees - presumably so you can insert and turn the board upside down without it falling out.