Teleprompter recommendations

I want to buy a teleprompter because I am going to make a series of short videos.

I see a number of them available for under $2500 and wonder if anyone has tried any of them and what you thought?

I plan to get a 15" screen for easy reading, plan to use it mostly indoors, but might do some outside shooting, and have a Mac laptop.

Also, on one shoot, I saw someone use something that looked like a small rheostat to adjust the speed of the teleprompter, but have not seen anything like this for sale. Can someone tell me what this is called and where I can get it?

Appreciate your help in this matter.