CMOS sensors have come way down in price (for the camera) and LCD has also come way down in price (for the screen) so it's likely there are some out there that are $50. The resolution is not going to be that good on them, but when you are looking at a 2.5" screen, it really doesn't matter. As for suggestions, I wouldn't know where to look. Never wanted one of them on my car. I would always want to look behind me since cameras can freeze frame on you making you think there is nothing there when in fact, there is. But that is just me.

 

I don't have the mirror kind, but I do have a window mount with a 2.5 screen, and it does surprisingly decent HD video (for what it is). It cost me $35 when I bought it.

I looked on Amazon and found this:

https://www.amazon.com/Crenova-170-1080P-Automatic-Loop-Cycle-Recording/dp/B01FCU2CWG/

It's normally $89, on sale right now, highly rated. HD, 5-inch color LCD, front camera plus remote rear camera, and it does DVR with a G-sensor to it captures accidents! That's a smoking hot deal - wow these things have really come a long way in the past couple of years.