Help finding top sash channel balance guide sets

Hello! I'm excited to have found your website. We have a dozen or more single hung windows that are all breaking at the same time. The plastic that these top sash channel balance guides are made of is getting brittle after ~20 years. I can't find any numbers anywhere on our window frames themselves, but your site gives me hope we can find something that will work.

The channel balances are stamped "2430 DE. B.S.I." We need 2 sets of these to replace missing ones in 2 windows.

But most important, we need the plastic bits at the top, which seem to be called top sash channel balance guides. I've attached a photo of the LEFT side from one of our windows. We need 8 sets of both left and right parts. The parts are:

1 5/8" tall
5/8" wide in the channel
3/4" left to right (when facing the window
Top cap:
1/8" overhang on inside, 1/2" overhang on the outside, 1/8" overhang on the edge
5/8" down to the screw hole.

Anything that could be made to work would be welcome. I don't mind having to drill out the screw hole, for example, if there's something close.

Thank you!