I'm 99% sure that all the AUQ's use the same one. Here is what your OEM 2005 AUQ belt comes back as (you might want to bookmark taht site for future reference)
toothed belt<br/>toothed belt guard Leon/Leon 4 (LE) 2005 year Seat EUROPA 109065 spare parts
seat.7zap.com
As Rich said, I would get Gates, Bosch or OEM kit. Buy from a reputable place rather than ebay or amazon, as there are loads of counterfits out there.
Edit: Just saw Alexis has confirmed