I come across all sorts of stuff besides slot cards and I'm even saving coupons and some odd paper items these days. If anyone else is interested, here's a link to my Delcampe listings for hundreds of coupons, jackpot coupons, tickets, TITOs, nakpins, coasters and all sorts of other casino related stuff.

https://www.delcampe.net/en_GB/collectables/search?categories%5B%5D=20485&search_mode=all&excluded_terms=&term=-slot+-card&seller_ids%5B%5D=554914

You can use their search to limit the listings to just the things you're interested in like coupons, TITOs, etc.

And by the way, I have over 7,000 slot cards currently listed on Delcampe too.