I started collecting the battle mats, map tiles, and pawn sets that Paizo makes for Pathfinder and Starfinder. Some of the older Flip-Mats and map tile sets have gone out of print and become hard to find, and some pawn sets are now unobtainable at any price except in digital form (PDF or VTT).
I see you have the Haunted House and Wasteland Flip-Mats, which have become particularly scarce. It took me a while but I managed to get those two from small hobby shops and independent book stores. Desert Ruins was another one that was very tough to find. I even have the coveted Ambush Sites Multi-Pack, which has never been reprinted for the Flip-Mat Classics line despite being used in a number of popular Pathfinder Society adventures. Noble Knight Games is pretty good for buying and selling rare RPG and war game accessories like these.
Now to actually get it together and run a real game...