Mitch sells 2 options on his website: www.rush2112.net I don't know the other manufacturer.
You can either use the SC-C1 or the SC-H1 tuner with Mitch's stuff. Depends on your needs, the SC-H1 uses 5 volt power and has optical and analog audio. It's more compact than the SC-H1 but you will have to buy a car Sirius antenna. The SC-C1 uses 12 volt power and only has analog but it does come with a car Sirius antenna.