I have a brand new Nikon Spur optic and mounts onto a Picatinny rail; an RMR sight typically costs $800+.Would be easy to make, but I can't think why?
O.K. I looked up that site as I am not familiar with the Spur, Looks like most of them, you take the two big screws out, the pict rail comes off, than you just buy the plate for your gun, you sight will sit way lower. If the gun is drilled already, you may not need the plate , depending on the slide was cut for. What gun and what was it cut for, Factory done?