Frido is right. Strips in all kinds of sizes can be found in most (specialized) auto parts stores (not Halfords, or at least not here in Holland).
For some inspiration, click through this thread on the forum of our German friends.
http://www.audi-a2club.de/thread.php?threadid=976&sid=
It lasts for 4 or 5 pages and you will see 'chrome' strips and some pictures of the used materials and techniques.
Strips can be seen on this lower grille, but also on at the bottom of side and back windows, on the brake light lower edge and even on the service flap (just like Abt sportsline sells them).
Personally, I have had some 3 meters of flexible chrome u-shaped striping lying around for 3 or 4 months now. I haven't come round to trying to fit it yet, as I fear I've bought the wrong size and shape.
But, have a look at the pictures in the thread above and get some inspiration from there...!
Cheer,
Edo
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(2003 Silver 1.4 Tdi Exclusive(SE), 95bhp/235Nm chiptuned by ABT, black interior, sport seats, heated mirrors, JVC KD-SH909RB cd-receiver, Infinity Kappa 63.1 + Vifa on-dash tweeters, 12" Subwoofer on 300w Amp)