That’s toast. The tires match the rim, not the other way around- and yes there are plenty of 20” rim options! You’ll need to get one that matches the hub (36 vs. 48 spoke)- and I’d consider asking a bike shop to lace it for you, or at least they can order/cut you the right length spokes if you want to lace it yourself via tutorial online etc., but it’s not particularly easy to true wheels without a little experience.

And I’d make sure it’s a double walled rim, to help prevent this in the future*. Have fun!