Wow - haven't had one of these in a while. If I remember correctly (and it has been a while), the last time we bought them, they were part of a variety pack. I need to do some major shopping this weekend...so will keep my eyes open for you.
I just did a quick internet search and it looks like Root Beer popsicles still exist but they are only sold as a multi-pack (w/ Lemon Lime & Banana). To make matters worse, it seems like you can only buy this multi-pack in the US. I hope I am proved wrong as I am now seriously craving one of these!