Here's an alternate plan (for those who can't find it at Costco):
(1) Mario Galaxy 2 will surely enter the "Nintendo Selects", in some time.
(2) Follow the "Nintendo Selects" page on Nintendo's site, as well as Wikipedia.
(3) When they first announce that it will enter the selections, buy
a copy at Fred Meyers. (just make sure that the NS version comes out
within 30 days of purchase)
(4) The games have the same barcode, so this should work.
(5) After you confirm that the NS version is in stock, return to the store,
and ask for a return of the difference.
Here's a better plan: go to your closest fountain and try to pick up the pennies, nickels and quarters that people throw at it for wishes. Save $5 and just buy the game.