Trimble CU Adapter
Here's one, but it's stuck to something else:
As we run 5600 and Geodimeter equivalent instruments I kept a reasonable eye out for what is available and in say 4 years only saw 2 of these on ebay as adapter only sales. I think they were asking around $300. Other than that I'm fairly sure I saw a Trimble authorised seller offering them on their website, but that was probably 3 years ago - it may have been Korec (UK), or SITECH (somewhere).