For securing my Deauville when it is not in the garage, I use two methods. I don't like the disc brake type locks - even with the warning cable - because sooner or later, you'll forget it's there, and try and ride off with the lock still in place. This is likely to case damage to the front wheel or brake system.
Firstly I installed a "Cyclone" simple motion-activated alarm, this is about the size of a packet of cigarettes and can go anywhere out of sight. In my case it is fixed via its adhesive pad under the saddle area, to the rear mudguard, just aft of the battery. Whilst it can connect to any convenient live 12v power source and earthing point, I used the adjacent bike battery.
The alarm chirrups as a warning if the bike is nudged, but goes into full alarm mode if the disturbance continues, or if there is major movement.
You can obtain these from eBay.
The alarm is supplied with two key fobs and the sensitivity of the unit is adjustable.
If I have to park up in some other location I also use this cable lock, it's about 5 feet long and is an armoured steel cable sheathed in thick nylon, so it won't scratch.
This is one example on eBay but there are many varities, either a complete lock like this, or a looped cable to which you add your choice of padlock.
When it's not in use, it's easily carried looped around the top box rack.
