Section 108B. In a town in which a district has been created and is operating under a law which requires the assessors of the town to assess district taxes and the collector of taxes of the town to collect such taxes, such district shall annually appropriate money for the salary or compensation of the assessors and collector of taxes, which shall be in addition to the amounts fixed by the town for salary or compensation as provided by section one hundred and eight and shall also include additional compensation for certified collectors as provided in section 108P. The amounts appropriated for said purposes shall not be less than the amounts determined by the prudential committee of the district, or, if there be no prudential committee, by the commissioners of the district and the selectmen of the town. Said districts may also appropriate money for books, forms and other necessary expenses of said assessors and collectors of taxes in connection with the assessment and collection of such taxes.