You can check out Overtons.com, but by the time shipping is factored in, the price may be too much. But, they have a few different models to choose from. Check out Fleet Farm and Craigslist, as well.
Farm & Fleet sells them. Made by LARIN and cost about $60. Harbor Freight has the manual ones for about the same price. Don’t have a clue how much a mechanical one would be. When I was at Harbor Freight here in La Crosse, I didn’t see a mechanical one at all. I priced these out before I bought mine off craigslist for $30. I use my manual one to move my Tuffy deep-v without any issues.