Patching-Clear Plastic Uppers
Can patch with “tent window” comes in .5mm and .7mm, glues well with clear glue.
Otherwise patch with leather that matches’ the colours of the shoes or at least looks nice.
If the shoe is strappy, consider stitching a piece of 6mm black leather strapping over the tear.
You may also have to put a thin bit of lining leather on the inside to make the edges of the plastic comfy.