The outside shower parts are supposed to be available thru Airstream.
You should try your Airstream Dealer or contact Airstream direct. I
had heard that some dealers were giving these to customers after
complaints that this should have been standard and not an upgrade but I
have seen no proof of this. I bought my outdoor shower parts in
Germany at Westfalia - see below.
Westfalia offers some very nice fitted carpets for the front and rear -
look here: http://redirx.com/?3dzs under Accessories, then
Buying parts and accessories from Westfalia in Germany is possible but
difficult from here in the US. You need to contact someone at
Westfalia and work out a way to pay for the items: they do not do
online credit card transactions for US credit cards. These parts are
also not inexpensive.
Here is an alternative for front cabin rugs here in the US: http://www.midwayspecialtyvehicles.com/parts.htm#2. There are other US
carpet options for Sprinters but I have seen nothing in terms of fitted
carpets for the Sprinter Westfalia in the US - I ended up cutting my