Since it's a bit late to expect a set of ears and a tail to be made from scratch, I assume you're looking for something that's already made and ready for sale. I looked at a few similar things myself this year, and you have a few different options.
1) If you're not looking for anything in particular and just want a simple ear/tail set for Halloween, you might just want to consider looking on
Amazon or any typical Halloween costume store. There are almost always a couple standard cat or dog accessories available there. They will almost always be cheaper than hand-made items.
2) You can search around
Etsy for ears or tails. Accessories on there are usually hand-made, so they may be a little more pricey, but they tend to look better than standard accessories from a Halloween store. But be careful - some Etsy listings sell custom item
offers instead of pre-made items. Make sure you find something pre-made so you can hopefully get it shipped in time.
3) I'm pretty sure Terra still has several ears and tails available left over from a con, you can ask her about them if you're interested:
http://www.furaffinity.net/journal/3891018/There are other places you could probably find something if you're not happy with any of those options, but I hope that helps.
