Is it really a CR2450 or is it rather a LR2450?
You can use a CR2032 and a battery holder if you use a diode to prevent battery charging current from going into your CR2032.
As they are not designed to be recharged, nasty things could happen. But with a diode, it's OK.
LR2450 should be direct replacements, but I don't know if they are available.