Gary:
If you still have the metal frames for the porthole screens then you can easily just replace the screen material. Take one screen to Home Depot or Lowes or Ace and they will have screen material plus the screen roller tool ( different sizes, different width roller) as well as the rubber spline material, round bead that is pressed into the slot that holds the screen in place.
To repair your screen do this:
1. Buy screen roller tool
2. Buy screen material, finer the better
3. Buy screen rubber, spline material, that matches your screen frame where the spline holds the screen
4. Remove old screen and spline, you may be able to re-use the spline material.
5. Stretch new screen over frame.
6. Press spline material into frame groove and stretch the screen.
7. Trim when finished.
Here is the spline tool for screens
Hayden