A flat file cabinet is your best bet for long term storage. Check your local craigslist listings or Amazon.
On the cheap end of the spectrum, I think it's worth checking out an art portfolio bag. The size options of these bags are limited, which is really the only caveat I can think of.
That is amazing! There is a really great book, The Making of Slap Shot, by Jonathan Jackson that is totally worth the read. It's out of print now unfortunately, so it'll cost you ~$80 for a copy, but I would highly suggest it.
I know this is 6 months late but I'm just looking through the sub.
Mondo put out a gorgeous coffee table book with a chronological order of their releases. I appreciate it isn't online but it is a stunning book.
Miami Connection is one of my favorite RiffTrax. If you have Amazon Prime you can stream it here: https://www.amazon.com/RiffTrax-Miami-Connection-Michael-Nelson/dp/B076MH8TQT/ref=sr_1_1?dchild=1&keywords=miami+connection+rifftrax&qid=1621277098&sr=8-1
https://www.amazon.com/Audio-Technica-AT-LP120-USB-Direct-Drive-Professional-USB/dp/B00GA9COMM?th=1
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How's that one look? Xmas is coming. ;)
I ended up grabbing these top loaders off Amazon: https://www.amazon.com/gp/product/B004L17318/ref=oh_aui_detailpage_o03_s00?ie=UTF8&psc=1
It should arrive in a couple days, so I'll let you know how they work! You could always grab 1 or 2 and have the posters share a top loader. I've had good luck with these in the past.