I have two complete Johnny Ray JR-300 mounts.
They have been lightly used, and the electronics mount plates were re-drilled to accommodate a smaller Lowrance unit several years ago.
I also have a spare non-drilled (new) electronics mount plate.
Everything - two complete mounts, plus the spare electronics mount plate - $35 shipped within the contiguous 48 states.
Stock photo of the exact model.
All the best,