It looks a little weird since the mount is designed to also accommodate a full-size C-More "Slide Ride" sight, but it works fine and keeps the FastFire low to the bore.
The LSP rail looks close to Picatinney. S&W M-41 SCOPE MOUNT | Brownells
Or you could buy a Weaver #62 rail and just cut your own slots with a file. This is what I did for one of my 41's with an ADCO red dot sight mounted.