Some while back I mentioned our experiments with ice packs for cooling casks. I have now found a supplier of these things: Filton Brewery Products of Eastbourne.
They do a rather neat design which comes as a sort of dry flat pack, filled with a gel of some description. You soak these in water, then freeze them. They can be re-used a few times. They come as individual sheets, suitable for a firkin, or on a roll, to be cut to whatever size you need.
The drawback is of course that you need industrial size freezers. Alternatively, you need a big team of volunteers to take them home and freeze them. I'm told by a landlord who's used them (at Jackson's Boat in Sale, Cheshire, which is having a mini beer festival this weekend) that you should buy 3 for every cask, so that you've got one on the cask, one in the freezer and one in transit between bar and freezer.
Full details at . They work out at around 4 pounds apiece. Filton's also do cooling saddles and similar (see ).
They will also hire out some equipment as well as sell it.