I have a Rollei/Nikor/LPL and searched eBay for months till some eventually turned up They are out there, and turn up now and then. I ended up buying the three (6x4.5,6x6,6x7) carriers. Maybe LPL in Japan will have carriers if your search turns up nothing.
I pulled out the styrofoam diffuser in the dichro head that was meant for 35mm and lined the area with thin styrofoam needed for the bigger neg. Very easy and the light was perfectly even on the print.
Jeff
Just saw the picture of the Rollei RDE. Exactly the same enlarger as my Nikor-Rollei.