I have a 06 VW Touareg. Do you know if I need an additional CAN-BUS interface if I want to connect my AVIC-D3 to my vehicle's VSS?

Thanks!!!

Yup.

Country,

Does the SWI-PS and SWI-CAN accomplish this or does this require a third item?

If I do need it, where can I find one?

Those 2 will only do the steering wheel controls. The canbus for your car I don't beleive is availible in the US. Honestly I've never really bothered to look for it so I couldn't say where to get one from.