Try Resource Conservation Technology in Baltimore, MD for qa good assortment of plastic seals for windows.
'Flipper' selas are designed for double hungs, and they have a full assortment of seal for other types also.

Drafts indicate movement of air. This is not usually stopped by simple insulation. You need to find out where the air is leaking through and seal it.

Check around the outside of the window casings. This is often a source of drafts. The may be blowing through weathered or nonexistant caulking. You can seal these from the inside and/or the outside of the entire window assembly. When we first moved into our house whenever the wind changed direction in the winter, I caulked wooden trim, around the windows, doors and baseboards. It made a tremendous difference.

You don't want to seal up the storm windows. They let out vapour that gets trapped between the panes. What you want to do is stop warm moist air movement from inside the house getting through to the outside glass.

Where you have old leaded glass, the best way is probably going to be to add a pane of glass or plastic on the inside of the window. This is often done without adding another frame and is sealed across the existing window frame.

Your windows will not be operable with this system. If you need operable windows, you will need removeable interior storm windows.