Right now, you can purchase a physical copy of Metroid Prime Trilogy for Wii on eBay. You’ll spend anywhere between $35 for the standard version and $90 for the collector’s edition.
Today, Nintendo has released an updated, digital version of the compilation. This re-release can be played natively on the Wii U (rather than booting into the Wii menu). Note that this release emulates the original, so you’ll need a Wii Remote and Nunchuck to play (sorry, no gamepad support).
Oh, and it will only cost you $10 for the first week. The price goes up to $19.99 at 9 a.m. Pacific / 12 p.m. Eastern on February 5, though.