Iris cordovan belt
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First of all, let me go on record as saying that I think that this is a bad idea. It's a much better idea to go with something either complementary or contrasting. An exact match... not so much.
That said, if you insist, you should contact Horween directly. The do make belts, and since they are the cordovan source, they are going to be able to be the best match: http://horween.com/products/upgrade-your-everyday-belt/