Unfortunately not that I've ever found. I recently tackled this same request for a client and we came up empty handed. We tried to go down the rabbit hole of customizing Shopify's Buy Now buttons, but unfortunately Shopify doesn't provide any hooks to add additional information like an affiliate ID.
We're working on some other workaround solutions, but nothing to offer at the moment. Please update the thread if you come across anything in your research, and I'll do the same as well.