There are plenty of places selling those nowadays, because it's the same as 1951 Chevy. I believe there is even a HAMB Alliance dealer. Don't buy off the first place you find if they quote you something insane - it should be around $150-200 per side at most.
I believe you can replace the 2 piece gl*** in all 49-52 Chevies and Pontiacs with the 49-52 1 piece Olds windshield.