I need the channel and the white stopper of the channel

We'd like to have you start your search with looking into our 18-069 top sash guide. See if the parts' measurements should match up with yours. For your channel balance, it could be either or Series 351 or Series 390 channel balance depending on the depth of your bottom balance shoe. You will need to measure your bottom balance shoe and compare it to the two balances mentioned to decide which of the two would make the better replacement.