Finding the right size lids, in CI or glass has proven to be a real PIMA. 98% of the people selling on eBay don’t know how or what to measure so it is a real crap shoot. When you find one in the wild you don’t have your pot with you but it looks like it might work. Nah.
I wanted a CI lid for my #7 RM BSR chicken fryer. After a few of months decided to try a Century 7-8B. I got lucky. It fit! However the lid came with a #8 DO for $75 + shipping. Now the DO was useless so I took a chance on a glass lid that covered the top but was sloppy and streak laden in the glass. $35 on eBay. Nobody would give me $10 for this slight spinner DO with lid so I just gave it to a junk shop. Bottom line: that lid for the chicken fryer, that is almost a match except for 20 years, cost me about 30 hours and 3X what the fryer cost.
No lid = trouble.
Hilditch