A locksmith might sell them.
Michael’s Keys in Rowlett is one standalone shop I’ve done business with
And A-1 is a big locksmith/gun safe business at the SW corner of Parker/Alma.
Or call other storage places to see what their pricing is. I think I paid about 20 bucks for one to replace the broken one DMS had on one of our spaces last year. Dunno what happened to that after Pearce got them emptied. But since I never saw a reimbursement (not that I care), I should think that if somebody knows where it is, it wouldn’t be subject to the “Must be publicly advertised for sale” rules, and DMS could let you have it in exchange for a small donation in my honor…