Remington 700 xcr tactical long range 338 lapua box magazine

[gilk1]

I'm looking at buying a used hs precision stock that is factory on the remington 700 xcr tactical long range 338 lapua to put on my 700 7mm rem mag build but it doesnt come with the detachable magazine. Does anyone know where to find an after market mag the will fit the factory remington mag well? The factory mag is $145 and I'm not even sure it will work with 7mm, any help would be much appreciated.