I talked to Yakima yesterday, and the mounts that fit our crossbars are called "winged vertical mighty mounts" but they do not have them for direct sale, which the guy said means that either they are discontinued, or they are part of the exclusive-selling-rights agreement with Isuzu on this roof rack system.

On the other hand, when I talked to my local Isuzu parts guy, he said that he could not find just the mounts as a separate part set, and that according to the diagrams he was looking at, it appeared that the ski rack purchased through Isuzu attaches directly to the crossbars. Well, that probably means that the rack comes with the mighty mounts, but who knows? If JAFO posts his part numbers, I can check it out for sure.

Nevertheless, I think mbeach's solution is the best... cheap, easy, and secure. Thanks for getting the pictures posted!