I would definitely hold off and re-supply at the Coop in Drumnadrochit. Only down side is its on the wrong end of town from the pier so a bit more walking involved. The shop with the local post office inside (much more conveniently located across from a pub) has some supplies, too. Another alternative is to ship your package to the post office in Drum. Good Luck!

I spoke to the campsite in Cannich a few days ago and they will be happy to receive a parcel for me - perhaps that is a solution for you too?

Stayed at the campsite last year - nice place, friendly staff.