G2A, maybe, its russian (their website is in english) but their stuff is usually cheap as fuck as a lot of stuff is usually sold by the community (no idea how the Xbox Live codes are priced there, maybe they dont change much from other places). You can pay an extra dollar/euro/pound to use their safeguard or some shit, never really used it but the stuff that I bought was always working.
Already bought around 10 times there.