there are basically 2 bit to a press, and saddle - the bit that the wood sits in and goes forward and back, and the press, the bit that imparts the force.
The saddle you could knock up with a few bit of metal, for the press, you would need and powerful spring to apply the force, and a strong handle and threaded bar to compress the spring, you would also need the roller, which might be the hardest bit to get, but would not be too hard to run up on a 1/2 decent lath.
This is all theory of course! in practice it might not be this simple