The modified damage amp is in a dFb_Pickups.u file and that contains modified versions of the other pickups.  The dFb_Pickups file isn't distributed because other servers don't need our logo on health packs, CTF flags etc...  I did a batchexport on that file and removed the classes, sounds and textures for everything but the damage amp:

http://download.dfbgaming.com:9080/dFb_PickupsDA.zip

Add dFb_PickupsDA.dFb_Pickups to the mutator list in the command line (if you need me to create an int file so you can add it in the web admin- let me know).

I didn't test it so let me know if it works.  The file contains the .u and .uz file.