Silicone grease. Silicone oil. Lithium grease. All 3 available at almost any hardware store or hobby shop. What you want is silicone oil.
If you want local ideas, clarify your profile. Canada is a big place. Nobody here reads minds. You'd be amazed at some of the places where you can find supplies, and loval people will know exactly where to shop.
You can also use the search option, or check a thread in the Information section about the care and feeding of GBB guns.