Source for LPL 55mm Threaded Lensboard???

Does anyone have advice on where to get a 55mm Threaded Lensboard for an LPL 4500 II enlarger? Apparently they used to make them but they are no longer sold. The 50mm version is still available from Calumet, B&H etc. but not the 55. I need it for my 150mm Schneider APO enlarging lens. I was hoping to find one before going to the extemes of getting something custom machined.

Thanks,

John
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