Reddit reviews Carav 11-450 Double Din Car Radio Stereo Face Facia Fascia Panel Frame DVD Dash Installation Surrounded Trim Kit for AUDI A3 (8P / with Symphony OEM-Radio) 2003-2008; A3 (8P/8PA) 2008-2012 with 178102mm 17398mm/178102MM
We found 1 Reddit comments about Carav 11-450 Double Din Car Radio Stereo Face Facia Fascia Panel Frame DVD Dash Installation Surrounded Trim Kit for AUDI A3 (8P / with Symphony OEM-Radio) 2003-2008; A3 (8P/8PA) 2008-2012 with 178102mm 17398mm/178102MM. Here are the top ones, ranked by their Reddit score.
Usage:Fill the gap between original car and new head unitMaterias :100% Hight Quality ABSSuitable For:TOYOTA Yaris,Vitz, Platz 2005-2010 (Black)Inner Size :178*102mm 173*98mmColor:Black
Don't know if this one will actually fit your car, but that's what I got on a quick search.
I bought my kit from Amazon for my 06 A4. You can also try this site. I got my steering wheel kit from them.
Lastly, I would suggest also trying Audiforums.com for additional directions. If, Reddit isn't getting you anywhere.