Accessible Built-in pop-up plugin?

Hello. I manage several websites for a large school district. They all use WordPress. We have been trying to move towards making all of our school websites accessible. Several of the high-schools like to use pop-ups to force parents to see and acknowledge important information. The plugin these sites currently use opens a pop-up in a new window which is not accessible. I’ve been trying to find a good plugin that offers embedded or built in pop-ups which are accessible, but have yet to come across one that does not require a subscription. The district is willing to pay a base price for a plugin, but hesitates on subscriptions. Does anyone know of such a plugin? Thanks!