HP-41C square corners display.

[rprosperi]

The earlier 41C, 41CV and 41CX units with "square corners" are referred to as FullNut models, it's the later ones with "round corners" that are called HalfNut models as they contained a much simplified board with fewer components. The LCD displays for the 2 types are not compatible.

There is no longer any source for new parts, so your best bet is to purchase a "for parts" machine from eBay or other similar sources. Since the units aren't working, it's impossible to be sure if the display will work, but there's frankly little other sources. I'm told that if they are physically in good shape (intact on the outside and no extensive battery spill inside) that these displays are usually good.

Other experts will weigh in here with more useful advice, as I believe that not all FullNut displays are the same and you will need to install a new display module that matches the type your machine originally had.