Adapter - 13.5x1 LH with SIG taper to 1/2x28?

I've settled on YHM's sRx mount for a R9 on my 9mm SBRs and am trying to find thread adapters for my MPXes to allow use of 1/2x28 muzzle devices.

I'd prefer to avoid a separate taper ring - has anyone seen adapters with an internal SIG taper? Searching isn't turning up anything.

Thanks!

To close the loop on the project, I found M13.5x1 LH to 5/8x24 thread adapters from Kaw Valley that index on the muzzle face instead of needing a taper adapter.