Public Mobile claims to always seek new vendors and locations where Prepaid Payment Vouchers can be purchased.
Off the top of my head, I can recommend all sorts of places (in BC, anyhow) - Wal-Mart, 7-Eleven, Mac's, Best Buy, Otter Co-Op stores, etc - which already sell a variety of other prepaid cards.
Why not encourage the community members to offer their own suggestions? I'm sure there's plenty of worthy vendors across Canada which Public Mobile has never thought of. I think a "Refer A Vendor" Reward for each new vendor successfully brought on board could be a powerful advertising incentive, lol.