Bulk Barn (in the NE) carries the 1 dram (~ 1 tsp) LorAnn oils including Peppermint for $2.09 + tx [they are next to the tills]. PM Hobbycraft also carries the LorAnn oils and another type (non-brand name); both lines have peppermint I believe. I've only been to the one on 32 Ave NE, but presumably the store near Ikea would have them too. You could check the Wilton line in Michaels stores [cake making section], but those may only be extracts and I don't think they have a very big flavor selection.
ETA: Apparently there is a Bulk Barn in the SE (4889 130th Ave) too, and one opening soon on MacLeod & 92nd.