Notwithstanding Section 20355.1, and upon a finding by two-thirds of all members of the board that the proposed purchase in compliance with Sections 20355.1 and 20355.2 does not constitute a method of procurement adequate for the operation of district facilities or equipment, the board may direct the procurement of prototype equipment or modifications in an amount sufficient to conduct and evaluate operational testing without further observance of any provisions requiring contracts, bids, or notice.