Check out Custom Collars by CollarFactory.com.
I remember seeing it for the first time when it was linked from an adisc thread about collars. In their forum there's an enormous gallery of the collars they produce, the quality seems pretty good from the pics, and they allow you to configure your own collar in every single detail.
Oh, btw, I'm no collar expert at all, although I admit I spent a good half an hour browsing through their galleries... :tongueout:
Yeah, I'd just say the local pet store. They have some nice ones. ^-^ Usually they're a max of 14 inches, but you have to allow for about an inch of breathing room. I don't think they make cat collars bigger than that unless you buy online.
Do girls really have necks that much smaller than guys? I know we have larger necks than women do, but I would have said that most adult women had necks larger than 13 in. I had a 15 in neck when I was 14 or 15 (and 16.5 now in the US, although UK sizing is strange and I'm only a 15.5). Then again, I think my ex wore a cat collar sometimes (I know she wore a collar, but it might have been for a small dog).