1975 PO boxes-seeking missing locks

[02bmw76]

Hello, all. We recently aquired some PO boxes, 30 in a 6x5 configuration. Everything is almost there, however, the letter combination locks have been removed. The slide pin is still intact, but no combination lock knob mechanisms. I've attached three pics. Does anyone have any idea if I might be able to track down some replacements? Any information would be greatly appreciated. Regards, Jason

[Halflock]

I believe that those were refitted to use a pin tumbler cylinder. 7835YA-04-KD is the part number http://www.mfsales.com/book02/207-211.pdf
This shows a picture of the cylinder on page 210 ( there are only 5 pages in this link).

I could be wrong but I have seen quite a few of those converted.