Glass/ Pyrex lid for pyroflam casserole (Meppershall SG17)

I broke 2 lids and l have 2 pyroflam (heat resistant) casseroles l use continuously in the microwave oven. The casserole opening is just under 8 inches wide/ diameter so the lid inside rim would be around 7.5 inches diameter. I have similar lid that l use for 3 casseroles which means l can use only one of them at a time. Many thanks