I've never given thought to matchbook covers as collectibles. Although, when I think back on it, over the years, I have made it a point to keep them; from bars/pubs, hotels, casinos, restaurants etc.....and I'm not even a smoker.
At some point, they always seemed to get tossed in the trash eventually.
I would likewise think old matchboxes would be quite the catch. Those are like a trip back in time. Have you had any luck using OfferUp to help you?