That camera disappeared from the market more then 30 years before I got involved with Linhof. Anything may be possible but we never saw or handled a 23 to 45 conversion.
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If it's of any interest to the OP, I'm currently building a 6x9 to 4x5 converter so I can use my 6x12 back on a Linhof Technika 70. I don't always want to lug the 4x5 around when shooting with my Technika 70, which is great as a handheld camera, among many other things. Obviously it's not the most streamlined way of shooting 6x12 (or 4x5 - same Graflok mount needed) but it gives me an option for panoramas without having to bring a whole other camera along.
At it's simplest, a Linhof 6x9 rotatable back can be salvaged, a cone added to the back of it, and a 4x5 Graflok back added to that. Heck, you could probably buy one of those Horseman converter backs and mate it to a salvaged Linhof rotatable back.