His original 1976 Gibson Limited Edition Explorer is for studio use only these days.
Edge has 13 (at last count) 1976 Limited Edition Explorers. I was at GC Hollywood when Dallas bought # 12.
I am not 100% sure that the all-black Strat used for "...Streets..." is the one from the early years. It does appear to be the same all-black Stratocaster used for "...Streets..." on the last two tours. (Vertigo and 360)
My theory is that the original is not in use and that the one being used, once had a white pickguard. Working on confirmation (or not) of the theory.
Dallas shops for guitars for Edge all the time. He searches guitars for Bono and bass guitars for Adam too. There are certain things he's looking for, certain models and vintages of guitars for Edge / bass guitars for Adam. So some of the shops know that if a such and such bass shows up in their shop, call Dallas; that sort of thing.
Where does he shop? Loads of places. Pretty much wherever there are vintage guitars.