Hi Kristen! I'm sorry to hear about Pepper
I hope it's nothing major!
In the meantime, you can put his cage near the shower to create steam, or put a dish of boiling water next to his cage and make a "tent" over both things to keep the steam in, etc.
This should help him breathe a little easier while you wait for the vet to become available.
I hope that the visit goes well, keep us posted!