I love mine but haven't been able to find a replacement - the lady that I got it from on eBay seems to have stopped trading!
If you persevere in looking, make sure that you get one with the opening on the top then you don't need to fold the number - even the big ones fit. The side opening ones are a nuisance. If you have narrow arms you may need to adjust the elastic but it's easy enough.
I don't need a replacement yet but I thought I'd keep an eye open for a spare. If I find one I'll post a link on here