Anyone that has a "water jet" cutting machine can make you an exact duplicate.
Not sure what is available in
Mexico, but there are several companies in the US that have them for making custom windshields for cars, etc as well as general production cutting.
Tolerances when cutting with a
water jet are extremely close (in the .005" range I believe). I have had all sorts of material cut with one -
safety glass,
stainless steel,
aluminum,
wood - so plexiglass won't be a problem.
I think there is a company back East that overhauls
Lewmar hatches and has replacement "glass" available. Their prices seem a little high to me, but they have them as more or less an "off the shelf" item.
Good luck!