6cm glassless insert for Opemus 5 and other questions

Does anyone know how I can get one of these, please? I'm doing 645 but am not sure they did that size so I think 6cm sq would be ok if I could find one.

I bought the opemus 6 645 insert but it seems to be for a totally different neg carrier design.

I do have glass inserts for using with 6cm but am not clear whether they are anti-newton glass or not. Does anyone know how to tell?

thanks