It's a bit of a specialist thing and not something you can generally buy off the shelf. After all, there's an element of pyrotechnics involved, exploding bag etc. Probably need a licence for the thing and you'd probably get sued if you used it because after all, as everyone knows here in the UK, the criminal has far more rights than the poor sods they commit the crime against.
You could always organise 'shifts' through the night to watch out of the window, keep a megaphone on hand and then if you see anyone touching the car, open window, shout through megaphone that the police are on their way whilst chucking eggs/flour and a bucket of your finest urine at them! I'd do it even if it was 2.30am :devil: