Chelle, I get mine from Ace Hardware. Ours actually stocks it, but if they happen to be out it's no big deal for them to order it and they give me a call and I run into town to pick it up. I get the big bags also. I use alot of it. I add it to bagged potting mix or my own mix. With all the rain here it's important that anything potted has good drainage.
I know our Lowe's carries the smaller bags, have no idea if it's amped up or not tho. To be honest I didn't even know Perlite was offered in an "Enhanced " form.