Best bike lock (with bracket)?

[ShortShift811]

Purchased a new bike recently, lock I bought at the same time was garbage (low security cable-thingy, and the bracket designed to mount ti to the frame has broken already).

Any recommendations for a decent lock that can be carried on the bike?

I don't like having to take a bag with me, and will only be locking it up for half an hour or so whilst popping in somewhere for a coffee, not all day long in a city centre or anywhere especially hazardous.

[Viperzs]

What is the value of the bike?

[ShortShift811]

Paid £800, insurance replacement £1K. Would prefer not to carry a d-lock round separately if I can avoid it.

[Mr Will]

Kryptonite Evolution Mini

A proper D-Lock that's small and light enough to go in the back pocket of a pair of jeans. Comes with a sturdy bracket for mounting to the bike if you prefer to carry it that way.

Yours for less than £30.