When I had my P-car, it's collapsible spare looked too wide to fit the Bug's tire slot. Have you tried one to see if it'll fit?
You could get any early 5½" steel wheel, including the spare wheel from late cars. Then put a 145 or 155 on it. That should fit. Then you don't need to carry a pump and wonder if it'll work.
Another option is to buy one of those Flat Four Fake Four-n-half Fuchs and put a 1-Fifty-Five on it. That's what I carry.