Fire up Multiman. Resign that EBOOT. And remember: Pride never dies.
You would need to search reputable "PS3 NoPayStation" or legacy "PS3 ISO/PKG" archives. Look specifically for the "3.55 Fix" "EBOOT patch" which was common during the Kmeaw/Geohot firmware era. Manual Resigning: Ufc Undisputed 3 Ps3 3.55 Pkg
for PS3 games were typically used for digital PSN downloads or game patches. UFC Undisputed 3 was released on Blu-ray disc, not as a full digital PKG officially. Fire up Multiman