Welcome aboard Jose.
As stated above, Ebay is a good place to start for the truck it self. Then there are several other places to get building materials and the like.
Tower Hobbies Has just about everything you could need.
Plastruct, Inc Has a wide assortment of scale structural plastics.
Garden Trucking "Precision Model Distributors" or PMD as we call it, has Tamiya hop up parts.
Online Metals Is a good place for getting metals is smaller sizes.
Scale Hardware Has some scale rivets, some bolts ect.
Micro-Mark Is a great place for Modeling Tools.
These are just a few links. Just about all of us here have a LONG list of links to just about anything you would need to build one of these trucks. If ever you need to get something all you need to do is ask, and someone will have a link to it.
~Mike~