There are sources that support immersion with a piece of cotton, coated with oil or Vaseline if necessary, inserted deep in the ear.

Since, however, the minimum requirement for tevilah is one momentary immersion underwater, and some ear problems can withstand that, and since the preference is not to have anything in the ear, these sources support use of cotton only when medically necessary. Ear plugs are less frequently permitted, when there is no other option.

See Shevet HaLevi 198:7:2 and Igrot Moshe Yoreh Deah I 98 (discussion continues 99-103).

You may wish to contact the Rabbi with whom you worked initially to see how he reached his decision. If it turns out that it is not a medical necessity, you could consider treating your phobia through behavioral therapy.

We hope this information helps.