Nope. That would be an augmentation of the appropriation and illegal. Ain't government wonderful? The only time donated funds can be accepted in the Executive Branch is if there is specific legislative authority to do so. Those authorities are usually quite specific as to purpose and use. A simpler solution in this matter would be for the GOP conferees to strip this amendment out in the House/Senate conference or even better, before final Senate passage.
How about a team of volunteers? Tax payers coming in to do work for free? (since we paid for this!)