PH wrote:This cheap one might suite your needs, I've used one to hold a fuel bottle in that position, but not for a while and I didn't have the issue with it fouling the chainring.
https://www.tredz.co.uk/.Profile-Design ... JSjfD_BwE#
Under the tube is a tricky position for a bottle cage.
One of my bikes has a Wilco bottle cage there - fastened on by jubilee clips (no mounts on that bike) and that works OK.
I can vouch for the Profile Design cage - I use it but not in that position. Clever design/materials engineering - seems like it will last for ever - if the cord goes, a bit of small diameter bungee will sort it. It allows a range of bottle sizes to be accommodated.
To be honest though, I wouldn't put a water bottle in that position - I'm not overly prissy but you never know what's being chucked up at it. For a fuel bottle, you can't beat the bike buddy. Takes a while to figure out the initial fitting but rock solid british engineering once you have (one time) sorted it.