Aspect Ratio Converter Box

I am looking everywhere for this answer. Not so easy, even for google to understand what I am talking about.

I am looking for a Aspect Ratio Converter box [ not computer software ] but an actual external box (size of a hard drive) that will convert 16:9 into 4:3 or any other customary aspect ratio format that I desire. As of now we are working in Standard Definition, but if there was such a thing as SD & HD compatible that would even be better.

The use for it: Transferring feeds and footage into 4:3/ vice versa so that we can send the whole clip/documentary in one complete format.

Any recommendations out there to as to which brand or box will do the job nicely?
I heard the brand GE has a good one but I cannot seem to find it anywhere

Thank you

All the Best!