i don't remember who the Techy Supplier inthe states is. You Might Try FG Hopups. or rcnuthobbies. maybe bigboystoysandhobbies.
The supercross is an XRC model. Try VSModelsport and see if they have parts.
The XRC car is a Knock off of a Technokit Jr... I don't know if the car is licensed by Technokit or just the usual Chinese way of reverse engineering everyone else's products....I'm confused, isn't XRC a chinese manufacture? Is this Technokit the same car you see on Ebay cheap?