I’m of the age where this is no longer a novelty item. Rather, an essential tool for weekends away, holibobs etc.

singletrack hip flask?

A full one

actually forget the hip flask, spirits come in screw top bottles anyway

Any that doesn’t leak the contents during use, and is a convenient size to carry.
Which pretty much describes any hip flask on the market.
Just do a google images search and buy whatever appeals.
I’ve got a Singletrack one, a Surly one, a long slender Jack Daniels one and an Art Deco James Rennie Mackintosh one, they each have their merits regarding size and shape.

Bikepacking spec hipflask.
Capacious yet packable.

Mountain Warehouse (that cheap outdoor shop) have hip flasks for £4.99, they are exactly the same design and make as surly/singletrack with the captive top but they do have mountain warehouse printed on them so nae style points.

Trouble with a metal hip flask is they don’t hold enough whisky, i use one of these

Just remember to tell everyone what achingly niche single malt you’re filling it with.

😉

Gentlemen’s Hardware Silver Hip Flask 6oz ‘Down the Hatch’ from John Lewis.

I had a Surly one but it sprung a leak, which was a crushing defeat as I loved it! 🙂

Surly there’s only one option?

Junk shop. Some classics there.
However a plastic 250 ml bottle is better in many ways. When you crush them they bounce back.