Based on my reading of DoD's two-part test (See DFARS 225.101), I think you are in compliance with BAA despite having to purchase $10K worth of stainless steel elbows from a foreign manufacturer.  $10,000 represents less than 1% of the $2M total cost that you estimated for materials and components for this project.  The threshold used in the two-part test is 50%, so you should be fine.  I would still check this out with your legal advisor because the rules in FAR Part 25/DFARS Part 225 can be quite complicated, so there could be other implications that go beyond my narrow reading of the FAR/DFARS.

DFARS 225.101 General.

(a) For DoD, the following two-part test determines whether a manufactured end product is a domestic end product:

(i) The end product is manufactured in the United States; and

(ii) The cost of its U.S. and qualifying country components exceeds 50 percent of the cost of all its components. This test is applied to end products only and not to individual components.

(c) Additional exceptions that allow the purchase of foreign end products are listed at 225.103.