alt Hacker NewsPass2U Wallet works great, but like many apps, it really should just be a feature to begin with.
The weird thing is that this was a feature when Wallet was first introduced. You could create a URL that would add a pass to a wallet. There were web sites that helped out with it. I still have some of the passes I created this way a decade or more ago.
Pass2U is neat because you can make somewhat arbitrary "Cards" with it. Cards with nice layouts that include QR code, images, titles, text, whatever. I have a card for my drone license, insurance, medical, and a few others. Super handy. It would be neat if they allowed that level of customization in the wallet app itself, but this is Apple.