Originally Posted by
neondave
Back in the mid 1980s , I had a cageless bottle , wish I had a pic or name. A special plastic mounting clamp with a 'V' shaped cutout , and the bottle had its own molded in 'V' shaped dohicky that slid into that clamp . Clean looking. The bottle finally broke and its the only one that would fit that mounting.

I once had this (^ similar?) bottle with integral frame adapter:
Made by RDR/Italy.
I found an expired auction on ebay:
RDR Cageless Waterbottle Made IN Italy Perfect ON A Fixie OR Singlespeed | eBay