That optic would work well with either a Raptor or an Alchin mount. Both mounts place the sight low on the gun. I've had great results with the Raptor mount and the owner is a forum member.
The 629 Competitor appears to have a Weaver rail, which the 1913 rail is derived from but not exact fit. You can also look for mounts that are marketed for early-style/California Desert Eagles, which use a Weaver rail.