I assume that
@seedy53 will chime in here with their latest supplier … but if I understand correctly *, you are looking for 2.5mm, whereas they are recommending and sourcing a mix of 4mm and 6mm. They are also using cubic zirconia rather than rubies/corundum.
(I have myself been prowling Amazon/Etsy/AliBaba/Temu for sources, but haven’t bought any yet, so can’t recommend anything specific with authority. But do watch out for ones with beading holes drilled in them, as those can apparently be trouble with cracking, etc., in heated environments.)
* “understand” from your corresponding r/vaporents post. **
** not that I’m following this all too closely, you know, across platforms, etc.