Replacement vinyl? strips which are used in old aluminum windows to hold glass snap/seal (triangular shaped)?

These are old aluminum windows with single pane glass held in and “caulked” using a gray colored vinyl/rubber type strip of material which is triangular shaped but has indented crevices so that the material snaps into place sealing the window pane. It is used instead of caulking. I don’t know if it is a glazing strips. It is 5/16″ by 3/8″ by 1/2″ and apparently could be cut into any length strips that you need. I have been unable to find it anywhere.