We're refinishing, reglazing and restoring all our old Marvin windows in a 1970's Wausau house - can you help?

Hello, we are refinishing and reglazing all of the old windows in our 1970's era home.  There are five different sizes of windows had a finished wood look on the inside, and some had a very weathered coat of primer on the outside.  I have no idea if this is how they originally came, but it does seem that they had never been refinished. We are having trouble locating a replacement for the weatherstripping.  A few pieces were salvageable, but much of it was missing or severely cracked. Thanks for any help you can give!

#1  JUST REMEMBER .. if your weather strip is that bad in "places" .. it should all be replaced ..

#2 Do all your repainting or staining first .. and be "careful" about getting paint or stain into the "kerf tracks" .. the narrow cuts into which a weather strip sets.

#3 Then install weather strip - cut at corners "as closely as possible to fit at joints without any "overlapping"

The part shown in your photo is here:  http://www.biltbestwindowparts.com/content/biltbest-casement-window-sash-weather-strip-leaf-seal-10

THE UPGRADE STYLE PART to replace above with  -  http://www.biltbestwindowparts.com/content/new-improved-awning-casement-sash-high-performance-seals