(gas) boiler problems

I have a Burnham boiler in my house, it's probably 10-15 years old. It has a draft inducing blower and a proving switch. So today I tried to turn on the heat for the first time this year and the boiler wouldn't light. I found the blower wasn't turning so I took the exhaust off, I then found the squirrell cage (blower fan/blades) had rotted to pieces and was getting bound up.

So here's my question. Where can I buy just the squirrell cage without the motor? I know the motor is still good, and have found it's quite expensive to buy the whose assembly.
Thanks guys.

F.W. Webb