E6500s don't like wheels that clamp onto the OEM sidewheel because it's thin, and there's a non-turning collar under it: if using a slot-over wheel the original sidewheel collapses onto the non-turning collar.
Jon H did a nice one for me that clamps onto the internal spindle. I have another E6500 with a wheel from Nick Murphy which is a sort of "wrap-around" jobbie. Both work well, so Jon H or Nick would be my suggestions.
Val has an E6500 for sale on the BBS with some piccies showing the NM type.