YotaAtieToo
Thick skull
Yes, obscure hard to find tires all the way around
I wouldn't say 17.5s are hard to find as long as you are at a shop that does semi stuff. Lots of low bed and equipment trailers use 17.5s.
But ya, probably not going to have them at Americas tire.
But like you said, a 16" tire and wheel should work fine for a spare.