Seeking Advice on Sealing Holes in Heater Due to Mouse Issue

I live in Marpole, South Vancouver, and the mouse issue has started again in my suite. The mice seem to be coming from the heater, and there's a lot of noise at night. I informed my landlord about sealing the holes in the heater, but he hasn't been supportive. Can anyone advise how I can seal the holes in the heater? Any contact number help would be appreciated.