While RB67 holders SHOULD fit ANY 2x3 GraflexGraphic with a Graflok (Heck the RB67 is a Japanese version of the RB Auto Graflex without the focal plane shutter, I have had the odd occasion where the Graflock back sliders where just a bit too tight. Most of the time they were Century Graphics. A file on the filmholder or a shim under the slider and it'll fit.
You had to remove the Graflok back on the RB (called the G adapter) to use the Polaroid back so those are a no go. But I think the HOrseman Polaroid back will fit.