You do occasionally see workshops advertised - keep an eye on the listings on www.salsajive.co.uk.
Most sane teachers don’t incorporate them into their normal classes for fear of encouraging people to injure their partners! I know Andy is planning a dips and tricks workshop as part of his forthcoming series - www.dancalatina.com.
Apart from that your best bet is to find a willing victim and book a private lesson (and don’t try any of what you learn on anyone without asking first - women can be easily be injured by these kinds of moves).