I had a look on Halfords site and I can't find it.....................if all you are doing is flatish surfaces (e.g. boot floor), you could use something like Marley tape/AquaSeal etc. You can buy it from B&Q.
I've had a look around as I have no experience of using Dynashield - the general consensus seems to be to use solid sound deadening over the spray; the spray wasn't very effective at all.