Hmmmm well, I would say Tanaka would be the best bet to look to for something like that.
The Tanaka m629
http://www.specialairsoftsupplies.co...&productId=460
Which kinda sorta looks like it. Sorta kinda not really the more I look at it the less they look at like
HOWEVER! the Tanaka Smith & Wesson M500 looks alot more like your posted pic.
http://www.justpistols.co.uk/m500.htm
Neither are exact but they are the closest I could find for you.
If the front end on the M500 was different it would be pretty much bang on.