T&T: Weatherstrip for Opening Rear Window

[Bob/Myrna Siegel]

Vessel is a 1990 Marine Trader Sundeck.  Rectangular opening windows in
transom area labeled "Jai Her".  Need new rubber gasket to keep window
watertight.  Am reluctant to remove old gasket until I know or a source of new
stuff; even better until I have new gasket material in hand before starting
job.   Alternatively, does anyone know of a way of "rejuvenating" old gasket
to restore weather-tightness? Thanks Bob Siegel; Annapolis #1869