I think they are called clippers!
The growth retardants have been withdrawn from the market, presumably because of safety concerns.
"Until two years ago I had used a growth retardant on my privet hedges called "Cutless", formerly made by ICI. Now I've been told that this has been withdrawn from sale. Do you know of a substitute growth retardant for privet, please? Pete Blagden, Berkshire
There is no replacement and, according to Guy Barter at the Royal Horticultural Society, there is never likely to be one. Just make sure you don't feed the hedge. I used to be able to get away with an annual clip for my privet hedge in London which was planted into worn out soil".