How to add an ID card to Apple Wallet from a photo?

I lost a membership card. The company sent me a “digital” temporary card, which I saved to Photos. I would like to add that card to my Apple Wallet and use it there until I receive the replacement physical card. I’ve tried adding it from within Apple Wallet and from within the Photos app, but neither gives me the desired option. This seems a fairly straightforward and simple request. I found the official Apple support article for adding cards to the Apple Wallet and see an option for using “messages,” to do so. I tried sending the image to myself via message and still can’t get it to work. Why is this so hard? I’m not trying to add a credit card to Apple Pay and don’t expect anything “scannable” at a register. I just want an image in my wallet that I can pull up and show vendors. In Photos, it gets more and more difficult to find with every photo I snap.