Cafe stop bike lock suggestions?

Hi All, 

I appreciate I’m asking for the impossible here, but I’m sure many of you have looked for the same thing so I’m interested to see what you found…

I need a small, lightweight but sturdy lock to secure my bike while going for a mid-ride coffee/pee etc. The bike won’t be locked up for long so I’m willing to compromise on the security of a D-lock but would like it to stand up to a set of pliers/side cutters/other pocketable tool. I know the right tools will get through any lock but it’s the opportunists I’m trying to avoid. 

So what are my requirements? Well, I’d like it to be:

Small and lightweight – I need it to either fit discretely into a jersey pocket/saddle bag or attach unobtrusivley to the bike (I know most locks come with a frame/saddle bracket but I don’t want a boat anchor swinging off the frame, or to be mocked by the cycling fashion police…)

Sturdy, as above anything that can resist a pair of pliers/side cutters should do – hopefully nobody is carrying round bolt cutters or an angle grinder…

Coated in plastic or rubber or something so it doesn’t damage my frame…

Cheapish – I want to keep my bike safe but anything so small and lightweight is likey to get lost 

Big enough to fit round the average lampost – no point locking the bike if it’s not attached to anything!

I know there are several locks out their that seem to fit my criteria – but I don’t want to waste my money or risk my bike with something that doesn’t work!

I’ll also do the usual, keep it in eyesight and next to a nicer bike – shouldn’t be too difficult!

Thanks in advance for any suggestions!