3M makes a lead foil tape which I have seen used to mimic the lead came of a
prisma glass storefront transom, should work here.

3M™ Lead Foil Tape 422
                          Dark Silver, 5.9 mil (0.15 mm) lead foil backing with
acrylic adhesive that
                          offers outdoor and long aging performance
characteristics.
                           ADDITIONAL INFORMATION  A good general purpose
                           moisture barrier, electroplating maskant and
                           sealant. Applications include decorative simulated
                           lead-glass window appearance from both sides
                           of tape, while providing resistance to weather and
                           sunlight giving long age performance.

                                - From 3M's Speciality Tapes amd Products
Division.



--

F. Mitchener Wilds, Senior Restoration Specialist
Restoration Branch
State Historic Preservation Office
919/733-6547
http://www.hpo.dcr.state.nc.us

***My opinions may not be those of my agency.***