Well I wouldn't really call it modding, but instead of getting some of the options at your Scion dealer, save a buck and do it yourself. Part's are cheaper here.
PartzNet
Toyota Parts 4 U
The TRD shift knob, TRD Air Filter, TRD Lowering Springs, TRD Shocks and the TRD Rear Sway Bar are cheaper at Toyota Parts 4 U.
*Update*
Toyota Parts 4 U now have more parts. I think they have everything Partznet has. Partznet may have certain items cheaper, and vice versa. If your trying to save money by purchasing from both websites, make sure you tally up the shipping cost to see if its worth purchasing from both vendors.
PartzNet
Toyota Parts 4 U
The TRD shift knob, TRD Air Filter, TRD Lowering Springs, TRD Shocks and the TRD Rear Sway Bar are cheaper at Toyota Parts 4 U.
*Update*
Toyota Parts 4 U now have more parts. I think they have everything Partznet has. Partznet may have certain items cheaper, and vice versa. If your trying to save money by purchasing from both websites, make sure you tally up the shipping cost to see if its worth purchasing from both vendors.