That chip says it uses a funky "Pattern match register" to access the RTC data. The chip I picked just maps the RTC into a few bytes of the ram itself.
When you say zero success, what did you try and what failed?
Did you put it in U36? You had the "ROM" version? was it blank? Did you bank in the U36? I would be very interested in hearing more about what you tried.
Yes, I had the ROM version, put in the U36 socket. I tried with and without adding a ROM chip with some (working) utility software on top of it and wrote some assembler code to set and read time from the RTC, following the official documentation I found on-line, but it never worked for me. Again, it could be just me: I'm not an expert at 6502 assembler programming at all!
I think that Miro wants to keep his RAM expansion board connected to the cartridge port and at the same time have an easy way to experiment with custom ROMs without opening the case everytime. That's why he's looking for a 1750 (REU + ROM socket), IMO
I have both a plastic one (with a clip-on hinge to open without completely removing it) and a fabric one. You can buy the fabric one from Vesalia, the plastic one sometimes appear on eBay (there's one on auction right now, look for this item #: 151875856851)