Um...you should try going to any independent game stores in your area, punq. There were a chain (of two stores) called Playsource in my area for some time, and they sold the original Game Boys for under $5. Hell, I think I've seen a few of them marked for $1.
The chain is gone now...but I've seen sales like that in other stores. GameStop and EB don't have the old Game Boys, but smaller stores might.
If not...you'll find one somewhere. I've got three of them (original, yellow, and clear)...and I wouldn't trade them. It's nice to go back sometimes, even though it's been a while since I've done it...