4-post shelf for 4-post 19" telecom racks?

I have a 2-post telecom rack (19" 10/32 threaded round-hole rack) with a 4-post add-on kit turning it into a 4-post round-hole rack.

I'm looking for a 4-post shelf with adjustable depth that will attach to round-hole racks with 10/32 screws...

I need to mount 2x tower servers... don't ask.

Thoughts?