Replacing sashes in Thermalator windows

Hello,

I am working on a renovation for a customer and would like to replace the sashes in a thermalator side-by-side vinyl window unit. The sashes measure 20.5" wide and 55 7/8" high and they are about 1.5" thick w/ double clear glass & dark brown frames. I need two of them for one window. I'm hoping that this is a stock size and I can just buy them and pop them in, or that somebody can make them for me. I have no idea how old they are.

Thank you,
John Nasta