It's important to remember that anything you buy/use is specific to YOUR trailer. Make sure you understand what you need before you buy.
I didn't want to drop $600+ for a set of Race Ramps so I looked around and found these:
Amazing deals on this 2Pc 1000Lb 9In X 72In Steel Loading Ramps at Harbor Freight. Quality tools & low prices.
I then cut two 4x4 to the height needed (6") to get my trailer door to the "correct" angle, then just set the Harbour Freight ramps on the "lip" that is on my trailer door. NOTE: You CANNOT drive the car onto these ramps in this configuration.
Here is the "finished" assembly.