... I installed mirrors to try and keep me from looking back so often.It might be to your benefit to do something like that. I know I like to see whats happening behind and nothing beats looking back, but lots of times a quick look in the mirror was enough and helped , keep my neck from getting really sore.
Sounds like a good idea.
If those tractors have a cab, maybe one of the cheap rearview cameras that they have now would work.
Here's one possibility:
And if that don't float yer boat, there are a lot more to choose from: