Dude you can get hi-capas for pennies compared to what we pay here in Canada so why not go and get yourself a TM hi-capa? Honestly though. A 5.1 Hi-capa is $150 USD for you whereas we pay ~$330.
As for the gun itself it looks like you might have to do some fabrication yourself or find someone who can do it for you.
Talk to Illusion about your project and I'm sure he can help you out. He has pretty much everything you need/want.
http://www.airsoftcanada.com/showpos...82&postcount=4
If you have the money I'm sure he can get a custom slide for you with everything you want on it. As to the grips it's probably best if you free hand that. Unless you're **REALLY** good with an airbrush you can probably stencil it in with a kind of fading/overspray effect.
EDIT: Airsoft Extreme is probably your best bet as to parts and such since they're in CA too.