I suspect the answer is no.

In particular I'm looking to play Fire Emblem: PoR which is very hard to find but my local store finally got a used copy.

I have a GC controller but that requires playing on the floor instead of the couch, something I will not consider especially given the long playtimes involved in a FE game.     Wireless GC controllers and an extension cord are also impossible to find. Checked already.

I fell in love with FE from the Wii's FE:RD and would love to add this to my collection but needing to use the GC controller would be a deal breaker.

Please say yes.

No, sorry. No Wii functionality in GC mode.

No unfortunately, and you can hardly find fresh ones out there; but if you can buy some at play-asia.com from japan since they still manufacture them for the wii. Just a suggestion.

You looked on eBay?

http://shop.ebay.ca/?_from=R40&_trksid=p3907.m38.l1313&_nkw=gamecube+wavebird&_sacat=See-All-Categories

http://shop.ebay.ca/i.html?_nkw=gamecube+extension&_sacat=0&_trksid=p3286.m270.l1313&_dmpt=Video_Games_Accessories&_odkw=gamecube+wavebird&_osacat=0

I fleeced a friend of mine for his extra controllers because he wasn't using his GC anymore. Yours is a good solution, though mine is cheaper if possible.

Did you check this? http://www.dealextreme.com/details.dx/sku.19116

That's an idea.   But to buy a controller for one game?    I suppose I might, might, play some N64 VC games with it but that's unlikely.  Nor are there other GC games I'd be enticed to play.  Maybe Soul Calibur 4.  Or Burnout. Or... oh no... I don't need to start adding GC games to my collection.  I spend too much as it is.  lol.

There are also some Wii games that can be played with the GC controller. SSBB for example, most people (that played SSBM mostly) even prefer it. I never owned a GC but I have 2 (3 but 1 isn't working very well) GC controllers. I did play SSBM a lot though. Sonic Unleashed also supports the GC controller (I've played it that way).
FE:RD also supports it , but the controls are simple so I just played it with the wiimote (+ its wireless).

^What about an extension cable? It's like 5 bucks.

The extension cable looks like the streetwise option. I was going to post a listing from Play-Asia, but the item in bmmb1's link is lower priced.