Using a teleprompter with an external webcam

I'm also a fan of starting as inexpensive as possible and then working your way up. I might suggest that, depending upon how comfortable the SME is with being on camera, and how quickly they can pick up the technique, you might try a free online teleprompter tool. Simply type "free online teleprompter" into your search engine and you'll find a number of options. The method is to place the camera right above the monitor when recording. In this approach, the script is there as a security blanket vs. reading directly. I've gone this route on numerous occasions, but the key is memorizing the script enough so that you only need to occasionally glance at the screen.

If you do wish to utilize a physical teleprompter, the good news is that COVID lead to a lot of models hitting the market and now, with folks returning to work, the prices have started to drop.  They come in a wide range of prices, but from what I've gathered, just about any $100-$300 model on Amazon (such as the $199 Glide Gear) will do the trick. Most models now use the method of reflecting an iPad (which is using a teleprompter app).  The main consideration is typically the type of camera you'll be using (DSLR, Camcorder, Smartphone) and making sure that you can mount it to the teleprompter. I have an older teleprompter meant for DSLRs so I've had to get creative with mounting my smartphone inside of it.

As for teleprompter apps, most will allow you to import your script from an online service such as Google Docs, but that's one thing I'd make sure of before you purchase. 

I hope this helps!