You can't rent or even USE one unless it's under the supervision of the registered owner; some indoor ranges in Canada will rent guns for use on their ranges, but that's considered "under supervision". Your best chance is to find an owner in the locale of your aunt's farm, and see if they'd be willing to accompany you for a day of shooting (which may also require a provincial hunting licence; not sure about hunting regs, as they differ by province). You might be able to find a willing soul at
www.canadiangunnutz.com . HTH
BTW, where are you planning to go?