You will find Gobuki Rokuyake in downtown Susukino/Sapporo located in big Lafiler mall, just outside Susukino station. The lower floors of the mall can also be entered from the station close to the Starbucks exit.
This natural lifestyle shop is the only place in Sapporo I have managed to find vegan margarine (which is hard to find in Japan). Also stocks vegan mock meat and a bunch of other stuff.
The staff is quite helpful and nice, but speak no English. I don´t remember quite right, but I think they only accept cash.