Standard Wii consoles are getting hard to come by if you are wanting a brand new package, but there are options still available. Stores off the beaten path for electronics (Sears, K-Mart, some Wal-marts here and there) may still have them tucked away in glass cases, but they are becoming more and more rare in the wild.
If you live near a Fry's Electronics, you may be in luck if it's one of these stores (
they still have stock according to their checker online, only available in-store):
San Diego, CA 9825 Stonecrest Blvd
Houston, TX 11565 S.W. Freeway 59
Austin, TX 12707 North Mopac Expressway
Plano, TX 700 E. Plano Parkway
Downers Grove, IL 3300 Finley Road
This is all assuming you aren't looking for the first edition Wii, the ones that play Gamecube games as well, those you will only be able to find those either new on eBay or Amazon (really high prices by now for new), or if you don't mind buying used, options will open up to you. Try waiting for a good Gamestop sale (they had them for $39.99 this past holiday season), or check out your local pawn shops / thrift stores (ones with a good return policy).
You can also try posting a want thread here on CAG for a used Wii console, would get better prices than eBay for sure.
Or if all else fails, you could always spoil your nephew and wait for a good deal on a Wii U console, as they are mostly backwards compatible with all Wii games (except for the minority that require the Gamecube ports, such as DDR Hottest Party).