Mustangdriver, gotcha covered here on the west side of town! Or is that the west side of the world?
We've been hangar cleaning and downsizing to get this crazy PV-2 in the barn down here, and have pulled out a couple of things that may be of interest. Only problem I can see for you might be location, but as Gary Hilton would probably point out "That's why there are trucks."
I've got one really nice 26 x 6.6 skin here - F-86, T-33, etc. It's about 35 pounds. 1960s vintage.
Found a presentable 36" here, too - B-24 nose. P-38 main. A-26 Invader nose. Probably others. 1950s vintage. Maybe 45 pounds.
If you're really fixated on B-17 stuff, I have a couple of 56" mains still mated to B-17/B-24/B-29 wheel assemblies that have to come apart sooner or later. These tires are 1940s or 1950s vintage cotton blend/rayon stuff and while they look OK obviously cannot be re-capped or used for anything but static display. I have some oddball matched tread patterns - egg, block, ice tread, etc. These things are a moose - maybe 250 pounds each or more. Even a fat boy like me has a heckofa time moving 'em about if they get sideways....
I think the B-17 fix for you may be a tailwheel tire. I've got a few B-17 TW's back there and one of 'em has a 28" smooth tire on it that while complete and still relatively round, the rubber composition is about as hard as the proverbial Chinese math test. It's a AN marked tire, I think, and if I remember correctly they all had 1950 or -51 dates. I'll pop out the TW casting and if you want it, just take care of the shipping.
Years ago I bought a mountain of warbird tires and wheels from a scrapyard outside of Davis-Monthan AFB, Tucson. We lumped 'em all home and started stacking them and quickly observed how much room old magnesium wheels with junk tires swallows up. Solution? Take apart the wheel assemblies, pile in the back of the hangar and part with the tires.
In a short amount of time I ended up with a mountain of rubber. At the time there was a local tire shop I did biz with for the family cars and trucks, and one day he saw one of the small wheels in the truck bed and asked about it. Told him the story and asked him where I could dispose of the old skins. I think more as a courtesy than anything else he offered to accept them at his place and would send them out with his other junk tires to the recycler. Probably thought I had one or two small ones, or maybe that I'd forget about the conversation and not return. Man, was he wrong!
Problem solved... until one day I got a little bold and decided to bring him a 47" main from a PBY. It went from my hangar, to his yard, to the recycler and then back again to his yard. Recycler was a little PO'ed that someone would bring in a 20-ply sidewall tire that would have destroyed his machine, and this ultimately ended my recycling attempts.
I suppose I can't get a few beers in ya and convince you that you need some PBY or C-54 skins too, eh? Maybe you could suggest to museum staff a new exhibit - "The Wheels that Went to War" and we could start small with perhaps a BT tailwheel tire and move on up the line in size and scope!