vinyl window sash stop - lower sill

Hi -

I'm looking for a suitable replacement for some lost vinyl window parts. Pictured above, these snap into the bottom of the window casing providing 2 functions:
1) act as a stop, limiting the travel of the single hung sash in the downward direction, leaving a 1/2" gap between the bottom of the sash and the sill, thus enabling the same part to -
2) act a means for exterior water which has come down the window face to move laterally along the sill to the drain holes provided on either side of the sill, directing flow outside the window frame and down the siding.

The key (exterior) dimensions of the part are 1/2" high and 1" front to back, while the width need only be approximately 1" wide.

The lack of two of these parts on in the bottom of each sill - one toward each side - has caused the sash to be either become "cocked" within the frame or "suspended" by the latch at the top of sash cracking the sash's vinyl casing.

If there is replacement or substitute available, I would greatly appreciate your assistance in finding it.