I've seen two dealers for this engine in the U.S. so far. United Hobbies has it for $325, but is out of stock, and www.lsproengines.com
also has it, for $470 (yeah, same engine) I talked to a guy who had rated it on the United site and he really liked it, He sent me a video of it running on a test stand, sounded and looked great.. I'm looking hard at this engine for a build I have going. It's the narrowest engine I have found in the 50cc range. From plug tip to plug tip is 8-1/2", plug cap to plug cap is 9-1/4". The guy at LS Pro says he can narrow it even more by using a smaller plug and caps, at extra charge. I only wish the plugs came off the back of the cylinder instead of the top (angled) as my concern with fit is clearance above the engine to my cowl.

The only other one I can think of around 50cc is the Roto twin. Look at it on RC Showcase site.