A catalog sells replacement plastic back panels for 170 and glass back panels.
Miata door window replacement.
Later models may require a different method.
This repair may be undertaken by any careful moderately experienced diy mechanic although it involves trim that requires care to replace neatly.
This is a typical miata door assembly.
Situated on top of the door these trim pieces act as a seal between your window and door keeping debris out but letting water drain through normally.
Note that not all miata s will have the same door panel some earlier models may not have the.
On the lower exterior is a single weatherstrippingwhich keeps water out of the door protecting interior components of the door from wind and weather and creating an aesthetic appearance at the lower edge of the window.
Lubricating miata door windows lubricating the door window channels can make the windows roll up and down more easily and can prevent future problems with the mechanism or cable.
Use white lithium grease.
Mazda sells a replacement back window for 370 and that is just for the clear plastic part you then need to take it to a shop to have it installed.
This repair is performed on a 1992 miatain the photographs and example below.
I did find ads for replacement back panels with a new plastic or glass window but those were also relatively expensive.
It may not be necessary to remove the door panel to do an adequate job.