Secondhand Boett (keep checking Ebay, they do come up) or the rip off copy that Derby House have in the catalogue at the moment - thats under £100 and looks very similar to the Boett.
In my experience any thing else on the market doesnt work well enough.
I actually have a Boett which has hardly been used, am going to put it on Ebay. Pm me if you are interested. Not sure what size you'd want but mine is approx 6,6
x
I used a Boett on our itchy Shetland. Great at sweet itch prevention but limited shelf life - he shredded, and I mean shredded two in two years. You get a bag of fabric for patching if you buy new. There is an optional hood too, but it scared all his friends!