I was asked at the Chicago Faire about sources for EPROMs. Many of the Chinese vendors on eBay have either seconds (AKA midnight run) chips that have not been through QC and don't have the correct recognition byte. They also have patently counterfeit chips. As a result, 50% or more will not properly program. So, despite their low prices, you end up paying the same for each chip when everything is considered. For that reason, I routinely uncheck the "check ID" box before I start programming any chip. You can certainly get domestically-produced new, good chips.
Rochester manufactures new TI, INTEL, and other usually-out-of-production chips under license from the original manufacturer. The drawback is that they only make a production run when they get an order large enough to justify the run. The quantity that they offer is usually too large for an individual. However, a group buy might be a possibility.
Unicorn offers smaller quantities of genuine refurbished EPROMs at a decent price with free shipping for on-line pre-paid orders of more than $25. I have ordered from them many times and their chips program first time, every time and are generally top quality.
Of the Chinese vendors, IC-CHINA and Funkward Tech, have the best percentage of good chips. You will, however, have some bad chips from time to time. Both are on eBay and offer a fairly wide range of EPROMs.
Those are the experiences that I have had with EPROM/EEPROM vendors. You can also try Mouser, DigiKey, and Newark for a much more limited offering..
Edited by atrax27407, Wed Nov 14, 2018 8:12 AM.