I think so (unless your by-laws specifically prohibit it -- ours say something about funds may be carried over if earmarked for a specific purpose, and I would think that this qualifies).

Our PTO last year approved a large expenditure and it has now come to our attention that the purchase was never completed. The school is now coming back to us to fulfill the expenditure. We are now on a new year budget with new Executive Committee. Can we purchase it without taking a new vote?