Good Morning, Matt,
I'm going strictly by memory here: I think that Beseler does have a glass carrier for the 45 MCR enlarger; I seem to recall seeing one on E-Bay sometime in the past.
May I suggest, however, that the Beseler Negatrans would probably serve equally well. It's very well-designed and puts real tension on the negative. There are also only two surfaces to keep clean instead of six with a glass carrier. In addition, I've never had a problem with negative popping in the MCR-X, regardless of the size of negative or the carrier used, and I used the standard 4 x 5 carrier for many years before I bought a Negatrans. Maybe the heat absorbing glass is just doing its job.