Hehr 3500 and 3600 series Multi-Tork windows are nearly identical, with the 3600 series found on travel trailers and the 3600 series used on mobile homes of the same era.
This top seal is sometimes known as a jamb seal. It has a bulb approximately 1/4" diameter and the T for your channel is approximately 1/8" wide. The flap protrudes approximtely 5/16" off the bulb, which may be slightly shorter than your original.
Made from gray vinyl rubber like the original.
Original Hehr part number is 009-250