Does such a thing exist? I know you can get them for the 22.5"...
Yes, definitely. Your greenie should have them.

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Yes. Not sure about the thumbscrew style, but definitely the H-clip style.
I am guessing very late 1990s, and into the 2000s.
I had a set on my 18" OTP, and also an 18" OTG.
Quote from: Mr.CPHo on October 17, 2018, 08:21:40 AM
Yes, definitely. Your greenie should have them. 
OHHH... I assumed they were standard steel... they're kinda rusty looking, but they are still solid. Good to know... thanks Charlie!