I bought the 705 piston from Schnitz. Good stuff, good service.
I strongly recommend sending your cylinder to M-Tech Motorcycles (the folks that Schnitz recommends) or to Eagle Mike or to ANY shop that has done KLRs before.
I took mine to a well-respected local head/crankshaft shop and he looked over the head and sent the cylinder to a shop that specializes in motorcycle cylinders (but not KLRs). I could have saved $400, a month of time, and hours of measuring with micrometers and bore gauge by sending it to Oregon.