If you are not planning on showing the dog, I would absolutely him fixed. Perhaps the reason you didn't see any at your local shelter is not that there are none out there, but that both Border Collies and Aussies have a very committed rescue community, who will pull them from shelters as soon as they get there, because being in a confined space for any period of time can drive a busy herding breed like them over the edge toward destructive behavior, and cause longer-term problems.

I just Google "Border Collie Rescue" and cam up with a whole page of Border Collie Rescue groups based in various states and regions - and that's just the first page.

Go to http://Petfinder.com and type in your zip code and you can look for what dogs are needing homes near you!