Most of Harken's stuff is designed to fit their proprietary track, & to operate using ball bearings. Generally they don't sell a lot of pin stop hardware
in terms of volume out the door. But if your track is the 1 1/4" T-track variety, that's about 10mm high when bolted down, then a Shaeffer car may fit. If it's Harken
ball bearing track then the odds are slim to none. Click on the link for more info. Though based on your statements as to the car type, mixing & matching brands may work.
Edit: Here's the relevent Schaefer page if it helps https://hardware.schaefermarine.com/...jrn9l8ihj8jm24
You might also look at Ronstan, & Garhauer too.
One other option instead of replacing the car, is to reconfigure it so that it's position gets adjusted via a purchase
system. IE; set it up so that your cars are towable. It's a feature that once much sailed with, you'll likely not want to be without it. As it enables you to easily, & infinitely adjust your sheet lead position without having to take the load off of the sheet in order to move the car. Nor do you have to leave the cockpit
to do this. It's even better than having a traveler on the main sheet.
Less heeling, more speed. Ability to de-power, or power up the sail, etc., etc.