I have seen them for sale at the herbalist shops. Also look for them in the general stores, tech shops & the factory foreman in Tarant.
i have looked in all those places repeatedly and found nothing. its really annoying me because my explosives throwing dwarf cant use plastique!
As I remember, it is neither common or rare & will appear sooner or later, keep trying. If you have Teleportation or your own boat, they are great shopping aids. Best shopping method. Find a place 2 - 4 screens away from all the shops you want to look at. for Tarant& electrolite I recomond the far side of Kensington Park. F7, advance time to morning, look in the shops, if no sucsess F8 & start again. Saves the time of walking back & going to the next day.
wow, i never thought of doing that. it beats my method of running, sleeping, checking, running, repeating
Shopping is one of the great things in the game. I got a pair of girls hooked on it with shopping. I walked out of the computer room & one of them said, "been killing a lot of monsters?" "No," I said, rolling my eyes, "shopping. And no one has the right shoes," "WHAT, this I have got to see." and they were lost forever.