My first thought is why did he say the motor needs replaced? Very often these motors need nothing more than cleaned and possibly the brushes replaced. It's very easy to do, there are tons of tutorials on the net. I cringe when I see machines with wrong color replacement motors as most of the time it's been done for convenience and laziness rather than real need.
But, having said that, if you feel it should be replaced, new motors are readily available and inexpensive.
http://shop.sew-classic.com/Motor-Ne...s-SCE35L09.htm
Cari