In Shu"t Ohr Yitzchak (2:17:9) R. Yitzchak Abadi writes as follows:
Can one rely on the minhag of the world to use regular vessels in a one-time manner, and then tovel them? For example, if it is difficult for him to tovel them now, or for any other cause.
This question is very painful. Is anything that some people do or did called a minhag such that the rabbi then has to prove that it is not so? And then they will be upset at him and say, "how can you cancel minhagim, sometimes strictly and leniently?" And this is all because some people, empty and reckless, who do not know even one chapter according to its law, and would that they knew one parshah in Chumash, scream "minhag minhag" and therefore the the Torah is weakened. And everything that the pronounced rabbis learn all their years, day and night, some person comes and repudiates their words with the strike of a hand saying, "such is the minhag" and they all place a hand to the mouth.
And perhaps this too is what the Talmud in Shabbat (138b-139a) meant [when it said] that in the future the halacha will not be clear and the mishnah will not be clear in one place. And they mean to say that everyone will go after the minhag and not after the halacha and the mishnah.
Woe unto us that which has happened to us in our generation. Behold, in this generation yeshivot and students have increased, and yet they still only rely on the minhagim. And I would have to elaborate on this and to bring all sorts of minhagim that are opposite the halacha, and no [one] opens [their] mouth and chirps, and those who know this place a muzzle on their mouths because "a bit more and they shall stone me". And with the help of God "the vision is still for an appointed time".
(However, I will not refrain from mentioning one thing that I heard recently, namely that they brought out a new minhag to eat a pickle from the can without hand-washing. And despite the ruled halacha that something which is dipped in liquid requires hand-washing, they scream, "minhag minhag".)
And to the essence of the matter, to use a vessel that requires tevilah in a one-time fashion is certainly forbidden.