Originally Posted by GreaseMonkey
This. Bring one of the old ones with you as sometimes the pigtails have slight differences and you'll have 3 identical brushes in a drawer with different spring attachments. Also, sometimes they come in different lengths so measure the brush holder before you go. As mentioned you can sand them down but if you ever have had to actually do it you'll find it is not as simple as it sounds.
And if they don't have what you need at the hardware store, look up electrical motor/alternator rebuild places in your area. I have one across the street from my work that specializes in rebuilding power tools.
If you have a problem finding what you need, PM me and I'll walk over there next week and see if they have what you need based on your model number.