This looks like it would work well, but it’s a subscription. It makes no sense to charge me a yearly fee to make one pass file for my library card.

Look at Pass4Wallet - free from the start.

Commented in another reply, this is the answer. Works great and supports a dozen barcode types.

absolutely ridiculous. $10 for a single pass. I'd pay 99c for this app, and no more. Oh well, $0 it is.