SIG SHR970 doodads

[SADshooter]

My current go-to hunting rifle is a SIG SHR970 (synthetic) in 7mm Rem. Mag. Realizing that for the cost of replacement accessories I could buy a different rifle(s), where can I find barrels/magazines/non. magnum bolt? I've been pondering the addition of a .300 Win. Mag. barrel (realizing I probably don't need it) or standardizing on .308 to keep the M1A and FR-8 company.

Thanks.