https://github.com/NebulousLabs/Sia-GPU-Miner

Here is the source code. As far as we are aware, it works on all cards that support open-cl. The mining will not work with the master branch of Sia until the 'hardfork' branch has been merged. The hardfork branch is here: https://github.com/NebulousLabs/Sia/tree/hardfork

We are expecting to merge the hardfork branch either tomorrow or Tuesday.