heh
Don't stress it so much. You got another great looking male, you just weren't expecting it is all, lol. Like I said, if yo don't want o use your 5 gal. buy a 1 gal. (or bigger if you can find it) clear plastic container from the dollar store. I bought 5 the other day for a $1 each and they hold just under a gal. each (.962). I just put some holes in the lid with a hot skewer, put in some marbles and glass stones for substrate, and they were ready to go! They must love it in there because they all have a ring of bubbles around the edge, lol.
This is what it looks like, just that mine is a little more rounded at the top.
So I drove up to the other side of the outdoor mall and checked the dollar store. They have so much stuff in there I figured "why not." Well I found these great containers, so I could get all 3! They even had bags of glass beads and river rocks for $1! The jars really are great, they're 19 inches around and the water line is about 8 inches high, so the thing hold .995 gallons. All I have to do is a 50% water change twice a week and they stay nice and happy. 
I'm sure you could find something like this at a store near you, maybe not a dollar store necessarily, but somewhere. Also though, I remember a post Jaded made on another forum about a great little set she found at Walmart for "goldfish." It's a 1 gal. bowl with gravel and a plant for $7 or $8, so you might want to try that too. I hope you decide to keep him, IMO there's no sense in returning such a great little guy to an uncertain fate.
