I bought one on an Omega which I swapped to my Beseler 45. I then bought a faulty unit on a Durst L1200 to use as spares (it was only $200) only to find it was the later unit and completely incompatible with mine. I liked the L1200 so much that I swapped the good unit over to it. I've since bought yet another early unit on a Durst 138s (again, around $200) so I now have plenty of spares and two extra enlargers. The L1200 is a precision instrument compared to the Beseler, however carriers and lensboards are expensive and uncommon. The Beseler is a little more crudely built but the extras and spares are readily available and usually dirt cheap. They are also very simple so you could easily build a custom part with hand tools if you needed it.
Of course if you live in Europe this might be completely different, and Durst and Devere parts might be available in every corner shop. For me in Australia, eBay is my only source of spares. I have actually started modifying some of the Beseler carriers so that I could use them in the Durst and had built a replacement lens stage so that I could use the Beseler 4x4 boards instead of the Durst Lapla. I'm still looking for a Femoneg AM (4x5) to replace the standard Femoneg (9x12) and would like a 6x7 or 6x9 insert as well but most of these parts would cost me more than the entire enlarger so I may persist with the modified Beseler parts.