KWA has a couple of M92 offerings in their Professional Training Pistol line. I don't have any personal experience with either of these but KWA sells good products and their customer support based out of CA is excellent. All their replicas include a 45 day warranty too. Not sure what you would be looking for wrt upgrades (external/internal) but out of the box this GBB shoots pretty hard. There's a video in the last link that shows the GBB on the chrono, pretty impressive OTB.
http://kwausa.com/products_m9ptp.html
http://kwausa.com/products_m9tactical.html
http://www.airsoftgi.com/product_info.php?...roducts_id=3910
From the product description:
"The frame and slide of the M9 PTP is constructed from high quality alloy steel and is made to a 1:1 ratio of the real firearm it replicates. Weights are strategically distributed during production process to closely match the weight and balance of a real firearm. "
Sean
