You can buy all the stuff you need to easily make C64 cartridges from ebay, it's usually the guys selling the fake cartridges who'll sell the stuff to make your own cartridges... 
PS: I should know, I bought the bits'n'bobs to give it a try and it work perfectly... 
Agree. I wanted the C64 Ms Pacman Rom. Originals sell for $100s. A copy of the original Cart $20. Playing the game(that's what it all about).. Priceless.!
The exitation of the primate orbitofrontal cortex and amygdala producing tangent epiphytic recollections,,(sigh) doubly so.
