You may like to look around those models using Bay 1 accessories. The main reason being that this range of camera body is light in weight, cost of accessories is cheaper than Bay 2 or Bay 3 type. Although the f-stop 2.8 are better, but they are heavier & accessories cost more.
Those using Bay 1 accessories are normally lens with f-stop 3.5, I have a grey Rolleiflex T (Tessar) & like what I've told you, the lens is "bloody" sharp. Warning : you will sell your hassy stuff after comparing the result (no joke)!!
My recommendation:
1st choice : 3.5F Xenotar
2nd choice : 3.5F Planar
3rd choice : Rolleiflex T
E-bay is a good source of these cameras, the condition of cameras found in local 2nd shop may not be good, although I have seen some good ones in Ron-camera. But the price may be high, so good luck with Ron..
Regards
Tachi..