I have been tasked with extending an entry door that has been cut too
high. I need to add approx 2" to the bottom. The door is a true 1
3/4" thickness and I plan on screwing/glueing the extension prior to
filling, sanding and finishing.

The problem I'm finding is locating a material source that is 1 3/4"
thick that I can use for the extension.

I'm hoping that others may have encountered this same issue before and
recommend what I could use for material? Obviously all the lumber
I've found is 1 1/2" thick.

Recommendations please? Thanks