Where can I buy prodigy clothes?

Either online or shops.

Depends what type of clothes you want. T shirts are plentiful on ebay, price depends on age and style and whether they're official or not. There's also going to be some new stuff on the official site soon (hopefully!). You might even be able to find some in your local big music shop like HMV. Discussion in detail here:
http://www.brainkiller.it/public/forum/viewtopic.php?t=1763

There's also a pair of socks and an unofficial tracksuit top that occasionally turns up on ebay.

Last year some official Vans trainers came out which you can also find on the 'bay at around £40-50, two designs (hightop or plain sneaks) discussed here:

http://www.brainkiller.it/public/forum/viewtopic.php?t=1422

Also there was a backpack released in limited numbers (3,250), also discussed here:

http://www.brainkiller.it/public/forum/viewtopic.php?t=1205


Other than that, there's not a lot. They did do some pretty cool stuff years ago like a fleece and beanie hats and caps, but those are hard to find now.

BTW: Can someone explain me if this T-Shirt is official ???

I´m confused, cos of the AONO written on it BUT with the BGAT Logo ?

I´m not a blind person concerning official and non-official merchandise, but this shirt is available in a store here in Berlin that usually not selling non-commercial Merchandise

Could be genuine... there was an olive version available:
http://212.67.202.86/~theprod/dnacopy/dcrs/market.dcr (#5)

I own the olive version and it seems exactly the same except for the colour of course...

I would say that it is an official one...