Source expanded pvc sheets locally or you will pay an arm and leg for shipping.
I wouldn’t be surprised if they’ll sell them to you as “replacements,” but you could probably find locks cheaper from another source, even Amazon.
Not sure of Ap specifically, but the industry standard for glass thickness is 0.25”
Annealed glass is doable, but if you have a large boa or retic, I would go with tempered.