Better not - if You connect batteries together, always use same chemistry (OK in this case), capacity, state of charge, and try to make batteries at least cycled equally, if not just new.

Of course mixing types will work, but Your capacity will be limited to 2x less effective battery capacity, and even batteries of exact same capacity, but from different manufacturers, may age differently. It's just a waste of better battery potential.

I understand Your limited budget, but better save for 2x christgift's + mugen cover, than mix one new battery with stock nokia one. More cost-efficient in long term