There's an important distinction between whether or not a shop stocks an item and whether or not they carry an item.
Pretty much every LBS out there buys from the same pool of distributors-- QBP, KHS, Hawley, etc. If a distributor has it, they can get it.
Full bikes are the exception, because there are dealer contracts in place for all of the big names-- Giant, Trek, Specialized, etc.
Trek is only sold through Trek stores, Specialized often has exclusivity contracts as well (they will only be sold at shop that don't carry certain brands.)
But if the OP is looking for something less mainstream, like even say a Colnago or a Masi, there's a fair chance the shop can get it and just doesn't stock it.
I bought my Cervelo at my LBS and they don't regularly stock Cervelo.
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