up to you, you can go to US, but you will need to fill paperwork, inform US fish and wildlife what day/time you are bringing a frog to Canada at least 3 days before your trip to make sure inspector would be waiting for you on a border.
I highly doubt it really make sense to go through all that for what you can get in basically any Vancouver store and if you count gas $ by Vancouver crazy gas prices it will get more expensive to get a frog in US for you