Yeah there are lots of big buckets but for small timers the only appropriate kind I've come across are packets example. Also I've seen multiple people on hydro forums say they use the regular granular forum, soaked, as a foliar spray.
But you can also find lots of other neo nic options like safari/active ingredient Dinotefuran, and there are more I don't recall off the top of my head.
I'm a fan of systemics for the greenhouse. Very little chance of killing anything beneficial, and I get to keep my plants. Imidacloprid is inexpensive, and my go to.