Want the metal version, and one for a real gun?
Get it from the same place the US retailers do.
lamp4us eBay Store
Click on the 20mm Weaver Scope Mount Rail For M4 Carry Handle 15A
It's <$10 including shipping!
I have one, it works well and it wont cost you an arm and a leg!
DO NOT RAG ME!
It's my daughter's 22lr. Yea, I know its on a flat-top but this mount allows her to use both iron sights and the scope.
I have purchased from these guys in the past and they are legit, above average for china made parts and their shipping is fast (~1 week to Florida) for as far as the item needs to travel. They mark every order with "gift" so there is no customs issues.
Look through their other items. Check out their faux ACOG's. The Chi-coms steal the designs of everyone and make their own. Cheap. These guys seam to find the better knock-offs.
They have a * canebrake * approval rating.