Catalog Binding (with Separator/Divider)

Hi everyone,

I have a catalog of A4 size (closed), A3 (opened).

I would like to insert 4 x 420gsm divider/separator into my catalog. However, understand that i'm unable to do saddle stitching unless the divider is in a spread.

Wondering can thread sewn solve the above issue, or is there any other ways to bind my catalog?

Thanks in advance.