help finging the right replacement weatherstripping

Thanks for reaching out to us, Sharon. Unfortunately, we do not sell a good replacement for this wool pile. I've seen it before, but we've never been able to track down a reasonable match. The issue is that kerf; all of our wool pile types install using a flat base, not a ribbed kerf.

One possible alternative is a bubble seal, like our 58-053, but my concern there is that it might be too big. Look it over and see what you think.

Profile drawing of the 58-053 bubble seal.

We very well may, but I'm not familiar with what kind of weatherseal that brand window uses. In order to narrow down the list of possibilities, we will need a clear photo of the end profile of the original seal. 

I know you said that it's getting brittle, so acquiring an undamaged sample will be difficult. However I ask you to try your best; if we can't see it in undamaged condition, we won't be able to check for a possible replacement.