Been using a product from Kiwi called "Camp Dry" to waterproof boots with mixed construction, like the leather/cordura blend you talked about. It is ok for breathable materials. I have used it on packs to renew waterproofing. I have a spray can of it, but, I think it also comes as a liquid with a giant cotton ball applicator on the lid. The spray can was about $6 at Walmart.