Repairing 1990s-era wood-frame storm windows

Hi, I've discovered some of my storm windows' plastic parts are damaged, and I don't know how or where I might find replacements.

One part is the plastic track that's set in the wood frame to hold the screen and storm window; it is set in a groove along the length of the top of the base of the wood frame. This piece has two "tracks": one for the screen, and one for the storm window. The two tracks are uneven to allow for water to drip down and out through a couple of square notches cut out about 4" from each end.

The other part is what looks like a spacer. It is shaped like a "t" but is only about 1" long. There are two of these in each window, set in a groove carved along the length of the bottom of the frame, each one is placed about 4" from the ends. I assume these are in there to allow water to drip out if it comes inside the screen into the sill. As I am repairing the wood frame, this part is breaking, mostly where it inset in the wood, since it is just a small, thin piece of old plastic.

Any help is appreciated, thank you.