Just spotted this @ 3DGPU.com:

Saw at Apokalyptik.com's forums that EvilEngine has posted a file (69.5MB) that contains 98% of the maps that were included in the beta 927 build of Unreal Tournament 2003 that can be used for the retail release that does't have these maps.

Download Unreal Tournament 2003 Beta 927 Maps For Retail UT2K3