It seems that you need something that can survive a bad day at a cafe stop where the bike is out of your sight & both be flexible enough to be packaged conveniently and wrap around odd-sized obstacles. Something with nice weight & price too...
Honestly from the top of my head you can find things like ..
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As an example. This is something I use to have for my "cafe" stops. - it's an alarmed cable-lock.
This one has a 12mm diameter cable, so it's a good medium size between fat and skinny, the cable length is 25 inches long.
It weights less than 290 grams and can folded into about an area of 20.25 square inch size by less than an inch depth.
Which is enough to easily fit into a jersey pocket. I recall being able to fit Two of these in one of mine, though it did get tight with two (but then again it was a cheap jersey.)
this costs, £10.00 and the most expensive thing on it, is the alarm. Which is very, very loud. Very loud. 110db infact, and the alarm was triggered by interference with the Cable, i,e, tugged, pinched, moved, etc and it worked like clock-work, always consistent.
Obviously you'd think for £10.00 there must be something you're missing, well the truth is you're not, the whole unit is very cheap to make so that's why it's not expensive. The steel used isn't the best quality and the majority of it is plastic and rubber to save costs and ultimately weight too.
But at the same time, the key/cylinder is smooth and doesn't jam, you can toggle the alarm on/off, it locks firmly and audibly and it doesn't feel like it will fall apart in seconds of a real attack.
But you must think surely this has no comparison of security against the £50 ottolock and you'd be right -- except if you was using it as a cafe lock, not an "overnight" lock.
Because you'd always be within earshot of the bike, as opposed to leaving it overnight outside where you couldn't hear it.
The thief would probably run too, because when the alarms going he knows you're on the way to see what's going on. - Also, thick cable locks can be quite hard to just "cut" cleanly in one go, even with short-handled bolt croppers.
So when you stop and think about it, you do get alot for £10.00