You should be able to find the adapter at most RV places, and sometimes at Wal-mart in their RV section (if ya have them in Canada).
What they call a dog-bone adapter (cause it resembles a dog bone) will look like this:
Prime RV Adapter, 30 Amp Plug and 50 Amp Connector With Indicator Light and Handle: Electrical : Walmart.com
Or you may find adapters that look like this:
You just want to make sure you get a 50 amp female to 30 amp male.
They also make a reverse adapter that will let you plug a 30 amp into a 50 amp power supply. It will have a 30 amp female and a 50 amp male. You want to make sure you get the correct one.
I prefer the dog-bone, as you can shut the door on the campground power pedestal when using it. If you use the second type, it sticks out so much, you usually can't close the cover......and put's the weight of the 50 amp cord onto the end of the adapter, which can sometimes pull on the plug not letting it get as good a connection......especially on older pedestals where the 30 amp outlet is a little worn