Two places to try - I only have the name of one
a) Iona Appliances (??) in Cornmarket St, aka Coal Quay, rhs going towards river, opposite Kyle St.
b) Don't know the name of the shop, or street. It's off Hanover St, near the Labour Exchange. Coming over Hanover Bridge, Labour Exchange on your left. Take first left and shop is a few doors up on right.
If neither have your bags, they should be able to order them or point you in the right direction.