I live in north-eastern Arkansas and I need to know where I can puchase AQUATHOL K or SONAR to control skunkweed. Somewhere near my area.

Do you mean Chara, it is sometimes called muskgrass. Identification should be your first step. Skunk Cabbage grows in wetland areas as well.
Robert B

you should be able to get pond chemcials at any local feed and fertilizer store. Robert gave you great advice, you need to be absolutely sure what type of weed you are dealing with before treatment. If you are refering to Chara you dont need Sonar for control. chara is an algae therefore you need an algacide (like cutrine plus or other copper based algacide) Sonar is a herbicide, not sure if it will even kill chara. even if it does that stuff is $1,500 per gallon. Cutrine is $30 per gallon, get my point. find out what you have first, then drop me an email. I spray ponds for a living, I'll get you going in the right direction.