I have a pet door on my slider which prevents my slider from closing completely, leaving a gap that allows air through.  In the winter, it's a REAL problem.  The doggie door came with weather stripping, but it was useless.  This  works pretty well for me, and, believe me, I tried everything.  If YOU come up with a better solution, please let me know, but for now, this is the best I came up with.  Because it is flexible, it bends as the door opens and closes, keeping a pretty good seal on the glass.