I use a bumbag with integral visor compartment. Works a treat and have been using it since I first got the Ducati. No underseat storage, so this does a treat for map, water, fags, earplugs, and clear visor to keep the cops happy.
Hello u! I've got a Ducati tank bag lying about somewhere (red). I used to carry my padlock and chain in that. It's a bit tatty. But you're welcome to have it if you think it'll be any good to you. It's no good to me now I've got just four wheeled beasts, so it's looking for a nice home. I used to strap it to my bikes with the chain so that nobody would walk off with it and so I didn't have to carry it around. Helps protect the paintwork from the chain too. Let me know if you want it. I'll drop it down sometime.
If some B*****d is going to nick your bike a disc lock is not going to stop em.
By leaving it in the garage I reduce the risk of carrying it on my person and possible injury in a spill, also means that there is no way I can leave it on and try to ride off.
If you feel the need to put a lock on your bike when out and about why not put a small padlock through a link in your chain. Less obvious so less chance of em seeing it to play around with it. Will stop em dead if they try to push or ride the bike away. Also less hassle to carry around.
In your pocket is a BAD idea, my mates son is in a wheelchair for life after carring a lock in a rucksack after a low speed crash, OK a pocket may not be as bad but a lump of steel can do a lot of damage.
Those clever French people at Baglux do a good range of tank bags, laerge and small for carrying stuff, failing that the suggestion of a bracket for Abus locks is good, or very small bag for the lock fastened to grab rail if you have one or bungee to the rear seat.