I started finding beakers at around GS70ish. I've found them in Pop-n-Pills crates, in air drops, and from the trader. But, I didn't see ANY until I was higher level/GS. I've not checked the config files to see if it's set up that way on purpose, though. It could just be an RNG thing. Try doing some of the T4 Infested quests. Just take your time and move slowly, clearing as you go. They're set up in T3 POIs so choose one you know well and pay close attention, take out as many as you can before they all wake. Works great and you get those T4 rewards.