where can i buy it? is it at walmart or some other craft store?
Yep. I found some at WalMart. Hardware stores should have it too.
I got mine at Walmart.
Hardware stores, dollar general, Walmart, and my local grocery store ordered some for me. Later.
Keep it spinning™
I got mine at a local hardware store.
Just ask them for Paint Thinner. If you say Mineral Spirits they may look at you funny.