You're not trying to melt the thing - just get it 80 ish C warmer than the shaft - hair dryer, hot air gun, carefully applied would work. I'm lucky in that I use a "proper" bearing induction heater at work for slipping half-saft bearings and collars on. If I can't find that, they go in the big oven (as do gear box casings if I'm doing it the other way round, bearing into a housing) or a small induction heater at home for warming seized items - have to be a bit more carefull with that though.It is separate to the rubber currently but yes it's got a rubber surround. Heating the bearing up is likely to melt the dust seal surely?
As others have mentioned, stick the shaft in the freezer over night and it'll slip on by hand.