SERPAs, 1913 rails, holsters....
I'd contact Blackhawk's customer service or LE sales office after the major holidays. I think they sell a regular SERPA for the R or rail type SIG Sauer models but check first.
FWIW; I bought a new SERPA holster(left hand) for my full size M&P 9x19mm with 0 problems. A few ranges & agencies have knocked the Blackhawk SERPAs but I think it's a training/operator issue.
The main point is NOT to pull the trigger when you holster your sidearm.
If it's a big problem, look at a SFS or ALS model. Safariland has been a long time source for holsters & gear to 1,000s of armed professionals.
The Kramer, Milt Sparks & Mitch Rosen lines are custom but will last years.