You may want to check out the ACGAM R1 gamepad. It works via bluetooth connected to a cell phone running Engine Driver.
It has been 5 years since i used them, but there are a few youtube videos on how to set them up. I am not sure if they make them anymore, but I do remember they were under $20 each. We got 3, one for each yard, and they were ok. Most people though preferred the regular throttle.?