Post-covid, they are pretty hard to find used, everyone and their brother is setting up a show, somewhere, someplace.
I don't believe Levi is in the case rental business anymore, Josh H. took over the business. Most renters are not looking to sell spare cases.
Looking locally is the best bet as shipping is expensive. Perhaps the local flea market or antique mall. But, there are a pair on ebay right now.. don't let the no key hold you back, you can either use them without the key as most are at their table anyway AND you can get the replacement keys pretty easily, the cases have the key number stamped on the case lock.
https://www.ebay.com/itm/18624061455...Bk9SR5TwoJGfYw