Where can I buy an "antenna pole cross bracket"?

I am working on incorporating the bike trailer hitch from moaibob into a project of my own. Unfortunately, I have not been able to find one critical component, the "antenna pole cross bracket" (at left in the image below).

I've searched Google, Google Images, Amazon, Radio Shack, my local Ace Hardware... Are there any hams out there who might know what this thing is called in the U.S., and where I might buy it?

Alternatively, if you can suggest a different way to attach the caster to a bicycle seat post (see the full I'ble), that would be equally useful :-).

gadget-man4 years ago
kelseymh (author)  gadget-man4 years ago
You have got to be kidding me! "Work"?!?! That is about as close to perfect as I could have asked. 1-1/4" pipe is exactly the size of my seat post, and 3/8" threaded rod is what the caster uses as a post. Thank you very much!
your welcome, if you get a chance check out the only instructable I have.