Ouch, I looked into this and I'm afraid I don't have any good news for you.
The watch is out of production; apparently Nike used to be pretty good about replacing those watches where the band had failed, but since they're not making them any longer, it appears that in the past they had been offering credit toward a newer model in lieu of an exchange. I don't know if they're still honoring that deal or not - you'd have to contact them directly to find out.
The only other alternative would be to follow the suggestion from another user here on iFixit and buy a non-functional one off eBay or something and swap out the electronics. I did a quick check online and it appears that most of them being sold for parts are because the band is broken, which doesn't help you at all. Other fully functional ones came up as well, and several of them were only going for about $25 used.
As much as I hate the idea of non-repairable devices, given the low resale price of a replacement and the lack of any repair options, I have to suggest that it's probably time to retire it to the scrap heap. If you really like it, then getting a used replacement should be fairly easy and inexpensive; otherwise it may be time to look for a newer model that hopefully can be repaired down the road.
I'd love to have any other iFixit users more familiar with this product be able to offer some alternatives, but that's all I can come up with. Sorry I couldn't be more help.