Stereo Jack Plate Needed

[PC Biz]

I'm going to pick up an old grill front Mesa 4x12 cabinet from a local GC, but it has a mono jack. Can you all point me to a place that has stereo jack plates? I'm sure Mesa would sell a new stereo jack plate to me, but I just want to save a buck. Wiring diagrams would also be helpful. Thanks in advance!