While at first glance this seems like a simple question, the sheer number of potential suppliers makes a useful response more challenging. Having said that, it sounds like you are trying to prevent overpressure on glass bioreactors between 3L and 15L in size. That being the case, I would recommend talking to the folks at Continental Disc. Their Sanitrx HPX product is available in 25mmm, so suitable for the headplate, and can have a burst pressure of as low as 10 psig, making them able to prevent shattering attributed to overpressure. Here is a link for your reference;

SANITRX HPX