I am working on a large poster to display my original Pokemon cards, but because of the size of the cards and the way I wanted them to be laid out, store bought frames are out of the question. The poster is not 100% done so I am not sure what the final measurements will be once I trim down the poster board, but it probably will be 49 inches by 29 inches. All of the cards are in sleeves, but I still want something over all of it to keep the cards flat against the poster. What kind of plastic or vinyl or glass (though I don't know how I'd cut it) would be cost effective (at most $25), easy enough to cut to size, and not a pain to apply (like with phone screen protectors, it is hard to get the bubbles out). Thanks!
A clear Mylar sheet could work.
Clear, moisture resistant, acid free and archival. And available in the size and price range you are looking for.