https://old.reddit.com/r/DivineTribeVaporizers/comments/kuji46/a_very_good_chinese_hydro_tubebubbler_attachment/

https://www.amazon.com/dp/B07PMWW4XH/ref=cm_sw_r_cp_apa_i_gf0-FbQ9NASTA?_encoding=UTF8&psc=1

I just got this one off Amazon today. It's 14mm and it fits perfectly.

YuanXiang, 14mm Handmade Glass (Black) with Titanium Tip https://www.amazon.com/dp/B07PMWW4XH/ref=cm_sw_r_cp_api_i_p1DMFb02P8KQT?_encoding=UTF8&psc=1. You will need a 14 mm glass tube that holds the titanium tip.