UKC

Are any UK retailers still stocking these? Nothings appearing in searches  

You could order them direct from the manufacturer, pricey though.

I made my own from some neoprene. Not as thick but more than adequate for most temps/uses.

Where are you going? They might be available there.

For a 1 litre Nalgene? I have one that has hardly been used that would be happy to sell. Drop me a message if you're interested.

Just use an old sock

Doing Hardangervidda! I'm sure they'll have something in Oslo. I spoke to 40 Below and they're keen to be stocked here but the product is probably a bit niche 

That works in a pinch but when it's -30 you need something more efficient!

Will DM you  

Two then and wrap it in your spare jumper

If you don't manage to source one you could consider the Nalgene insulated bottle cover.

https://www.elitemountainsupplies.co.uk/camping-trekking-c4/hydration-purif...

I bought one those in 2014 and the zip failed on day 1 of an expedition! Shame because it was really good at insulating. 

Somebody sniped my purchase from Graham (thanks a lot!) so anyone else that has one in good condition for sale I'm still interested.