About ten years ago I purchased 1 Gallon of MEK. I've used about 1/3 of it in that time.
It's available in paint stores, Home Depot etc. (I think a Quart will last a lifetime)
This stuff melts and bonds most types of styrene plastic. I decant it into a small glass bottle and use a tiny brush or a very very small squeeze bottle with a syringe type application tube.
It will evaporate in a couple of days if you leave the lid off the jar.
Nasty stuff, causes cancer in California etc.
In the small amounts we use I don't worry about it much.
Jim H