I only used the guns the kid had which looked real enough to get you killed.
There are aftermarket suppliers that sell the parts needed to make them look as real as possible. In the airsoft culture no one but a 10 year old would be caught dead with neon tipped rifle. (bad pun).
Airsoft AK-47 for sale:
http://www.evike.com/products/37093/
http://www.redwolfairsoft.com/redwolf/airsoft/AEG_AEP_Tokyo_Marui_AK_AUG_Series_Tokyo_Marui_AK47.htm
Here’s are some links to an airsoft forum where people are buying/selling/trading with photos.