I got my first RSST from Exhale Vapors. It had the 510 threading issue but they include a replacement base with the correct threading. Try contacting them to see if they will sell you one of the bases with the yhreading issue for the part you need. Otherwise I might be able to machine one out of delrin.
Wow! Awesome of you to offer dark! I'll keep it in mind. I do have 4 other RSSTs so I'm not too worried about it. I may try the pen idea or see what exhale has to say. But I hate just seeing it on my dresser unusable for parts. I may be PMing you.
Folks like you are what makes ECF great! Thank you!