New part number 0809-0173-1000
Old part number 809-173-10

www.depcopump.com 800-446-1656 
$26 for just one brush. Two required.

http://solarwindworks.com/Products/Solar_Hot_Water/solar_hot_water.htm
$35.00 for just one brush. Two required.

http://shop.torresen.com/ships_store/index.php?p=details&mfc=MARCH%20PUMP&sku=0809-0173-1000&frm=g
$35.10 for just one brush. Two required.