Internal time/date battery replacement 500D

The time and date reset every time the main battery is removed for charging. This model camera does not feature direct access to this internal battery. There is posting under "Canon 500D Hard Reset" of a possible solution, with photo, on a way to access this battery saying to pry out battery cover. But on my camera just below the main battery hinge I veiwed only two vertical slots but no horizontal cuts in the plastic battery box. If I pry on the vertical slots the plastic will break. Is the backup battery really located behind these two vertical slots? If it is, could the remaining horizontal cuts be made with a Dremel tool or something similar to access the internal battery? At this time Canon no longer offers service on this model. I have not found any alternate disassembly/replacement procedures.