In a weird coincidence I found an alternative.
The Specialized Zee cage and this Torq bottle
https://www.torqfitness.co.uk/acatalog/info_201.html
I have a Spesh Enduro and I fitted a Vivid R2C coil shock recently which meant a standard 500ml bottle doesn’t fit
I tried to find a compact one that wasn’t the YT one but couldnt so had to bite the bullet and buy the YT kit which fits.
However, I’m just using the Zee cage that I had before with the bottle. I was on a ride last weekend and found an abandoned Torq bottle and I thought it looked very similar to the YT, size wise.
Popped it in my cage and it fits perfectly!
Plus my mate with a Jeffsy uses the Zee cage as he broke the carbon YT one and they won’t sell the cage or bottles separately
TL:DR – Zee cage and a 500ml Torq bottle definitely works