Where are people getting small quantities of rubber window gasket material these days? Central Sales and Service is not a supplier so they don't usually inventory any of this stuff - they manufacture it to order. Which is fine if you have to re-glaze an entire car and have the budget for it. But what if we just need to change out one or two windows, and need new gaskets for same? After the demise of the late, great Power Parts Co, I recall using Logan Corp. But since WABCO bought GE, Logan doesn't stock those gaskets anymore.

Thanks in advance for any leads.

check with this firm, seems to have a large selection of gasket material

https://www.restorationspecialties.com/

Wholeheartedly endorse the recommendation to try Restoration Specialties. They supplied the rubber material used between the upper and lower sash windows and the seals at the window sill for Johnstown Traction Company streetcar #355 during its restoration in 2005-2007. They stocked material that was similar in appearance to the original and still functions well nearly 15 years later. The staff were also a pleasure to deal with and the price was reasonable.

I seem to recall using their products on different streetcar projects and possibly one of my antique autos as well.

Good luck with your project!

Best wishes,
Matt Nawn