Heater blower fan replacement

Quite a few of the plastic blades on the fan in my blower have disintegrated (made a hell of a noise the first time I switched it on!), the motor still works fine so I'd like to replace just the plastic fan blades if possible. Anybody know if you can buy just the blades, I have looked in the usual places but haven't found anything. Alternatively, has anybody got a blower that the motor has died but the fan is still in one piece and wants to get rid of it? I don't really want to have to put a bilge fan in unless I have to.

The parts book only shows the complete blower as a part - there's no separate part numbers for the motor or fan.