Looks like this is as good a thread as any for my own question.
I just got my first wordup order -- a 5 pack of ego cartos which includes a syringe. Yours is the best price I've found, thanks!
Thing is, the needle doesn't fit the fill-hole. I've filled a few cartos before so I'm fairly sure it's not user error. The wordup needle is blunt so I pierced it with an old needle, and even stuck a paperclip in there and wiggled it trying to make the hole bigger, no luck. I was able to fill it with my old needle.
The description didn't actually say it would work for refilling these, but I figured since it was included with the 5 pack it would. Could I have gotten the wrong needle?