Brushes stop turning as soon as there is resistance

\015 Belt is fine, brushes are fine, brushes turn fine until there is any resistance – have replaced the belt and the brushes and the belt cover – problem appears to be that the large sprocket that turns the belt is stripped – not sure if it had teeth on the inner circle of the sprocket where the belt goes. All I can see is that it is smooth. Need a new sprocket I believe but can’t order one from Bissel – not on the parts list.\015 – Bissell SpotLifter 1716 Bagless Handheld Vacuum