They are in very high demand at the moment.
I did a training course that included the usage of foggers. Fogger section took about 30mins max. Very handy bits of kit, and very good at cleaning a large area, quickly (think walls, ceilings etc). The one that was used in the demonstration was a B&G and it got to the roof of an industrial unit, while the operator was stood on the floor (industrial was like one that every town has an estate full of, maybe 4 metres high).
I did see on another forum someone selling 'smoke machines' as foggers, and then whining about his integrity whenever anyone said anything
. There are currently 0 decent foggers available through reputable sources in the UK. Second hand B&G (£450ish brand new normally) went for £860 on eBay yesterday.