In this recorded lecture, Rabbi Akiva Tatz mentions that R' Moshe Feinstein (who famously did not prohibit smoking, though see here) forbade a person from handing a lighter to a person who smokes because of lifnei iver. (contradicted by Shalom here)
Rav Moshe Feinstein says you can't pass the matches to a smoker [...] even though he [Rabbi Feinstein] doesn't rule absolutely that everybody has to stop smoking who smokes already.
(linked lecture, ~51:30)
Is this (or its inverse) a ruling that is recorded in Igros Moshe, or anywhere else "inside"?
Rabbi Tatz did not appear to plan to talk about smoking in that particular lecture (the quote appears in the questions at the end of the lecture), and perhaps erred in recalling that ruling.