As no one has replied i think you may need to add some further info, what kit (have you tried the kit manufacturer?) or details of the tug (year built, type (harbour/coastal/sea-going?).
Ad for fittings, try Westbourne
Model Boats At Westbourne-models.com
They should be able to advise if they do not stock them. Sorry to be so inconclusive but I know very little about tugs.
J.