That's a bit like Rudy K's vise is like and what I originally found. Problem is the 6" is the smallest and while this doesn't sound like a problem for you I think it's probably to big for my 7b where the table is only 6x6 1/2". The original vise is only 4", and unfortunately the smallest 2pc vise is 6".
Do a search for 2 piece vice, I know that I saw 3 & 4" ones when I originally searched for them. I think Shars might have them too