Buffy continued with season 8 in the comics (They are considered canon). It's currently on season 10 which they said would be the last season. I'd try www.tfaw.com or amazon.com
The 이전 poster's suggestion for tfaw.com is a good one. I've bought many comics from there. Another good option is Comixology.com if you'd prefer to buy digital versions rather than paper copies. It's a bit cheaper that way.
