Are you referring to the screw-on adapter that lets you use any 510 drip tip? I have one that I no longer use. If that's what you are looking for, PM me your address and I can send it to you.
Alrighty, so after an awesome member, PeteMoss, sent me a Russian 91% drip tip adapter, it doesn't fit!?! I have the original Russian 91% V1 (as far as I know) and this adapter is just a tad bit too small and the threads a tad bit too big, maybe this adapter is for the larger russian, or the v2? I have no idea, I am truly stumped. My best bet might to be get a new top cap, this dang part has become so elusive now I run the risk of buying a part that doesn't fit.
If anyone has any advice or info, please let me know, I still need to go back and read the last couple of pages, hopefully there is an answer!