I'm afraid I don't know what retainer strip you may need. Cole Sewell has been out of business for a long time now and there is a good chance that the piece you need isn't made anymore. If at all possible, I'd like to see a photo of the part in question. I'd also like you to briefly describe its function, just to ensure that we're on the same page.
Thanks, this is a huge help. So, we unfortunately don't sell retainer strips like this. They're hard to stock because every door manufacturer designs these in a different way. Considering that, plus the fact that Cole Sewell isn't in business anymore, and I don't think these will be easy for you to find.
The good news is that we have an alternative solution that should work just as well. Back in the day, storm door companies didn't even use retainer strips: they used small clips distributed evenly around the frame. They serve the same function and are much easier to replace, but they don't look as nice and they take a little effort to install to begin with.
My top recommendation is the 70-180 clip and 70-112 thumb lever. Installing these will require drilling holes in the door frame but they should work perfectly well for your application. Look them over and see what you think!
