Jrand, I have a lot of experience with clogged drains. A very cheap, low-toxic way is to use hot water. The water in my building isn’t very hot, so I have to boil it, but you may be able to do it right from the tap. I usually need about 8 quarts. Just keep pouring hot water down, as much as it’ll take at a time. It hasn’t worked every time, but it’s been great when I couldn’t get to the store.