Don't focus too much on the temperature hypothesis. The most sensitive SmCo have a guaranteed operating temperature of +250°C, others guarantee +550°C, wow. Thanks to the fan, they won't get that hot.
I don't really grasp the purpose of the design with magnets along the iron. Definitely less induction available at the tips. A hypothetical advantage is that some induction is available over all the radius, hence fitting smaller stirring bars too, and not just at the tips when the magnets are there. But for that goal, less bad designs would be easy. And if the stirring bar has the proper length, magnets at the tips stabilizes its position.
Anyway, if yo suppose that the magnets lost their strength (I bet they didn't), they are easy to buy and replace. Take any SmCo (there are only 2 big groups distinguished by their composition, take the highest Curie temperature) of proper size from eBay or elsewhere. Be careful with strong magnets: all knives away, all iron away, think before acting.