I use a Domke gripper on my 2.8D. I'm happy with it and it doesn't look too out of place. It works well around my neck or slung over my shoulder, it really does grip well!
I've not had a problem with my OpTech strap. I've had one on my digital camera for about a year and a half and really like it, I've never had it disconnect unexpectedly. IMO it would look goofy on a Rollei but its your camera, not mine