You might try (of all places) "Runnings", in Monticello, Mn. If your store is anything like the one near me, you might be in business. Ours has a surprising (!) amount of (various grades) metric hardware. Zinc plated, cad plated, hard chromed, chromed, and stainless. If that doesn't work, try a piece of metric all-thread, cut to length, with stop nuts at either end. Good luck, and let us know how it turns out (we're nosy!).