RE: .338
If you can't find a shop that stocks them on a regualr basis then just handle the 300 Win mags and find one that you like. When you do find one that fits you well and is in your budget have the shop order the same rifle in 338 Win mag.
Pretty much every manufacturer chambers the .338 Win mag.
Remington chambers it in the XCR. Surprising that it's only available in this single model.
Winchester chambers it in several model 70's.
Ruger chambers it in three different rifles.
Sako and Tikka both chamber rifles for it.
Browning chambers it in several A-bolts and BAR safari.