This probably won't help you out today, but you can get a Paypal debit card (unless they don't offer that to people in Canada)

Of course, a prepaid Visa should work too - you can pick one up at just about any store that sells gift cards & such.

(By the way, unless you don't want your mom to find out, you're pretty safe just using her credit card with her permission. I would bet Herbie's site is secure and no one's going to use that to track you down.)