Have you considered AI2s? They are very similar to pockets in that you can take them apart and many brands have options of boosters.

I used BumG pockets - they are one size - and found them excellent - thery were my work horse nappies and lasted perfectly the almost 2 years DD was in nappies.
Also used and loved Wrigglebumz (NZ site).

You can also make your own boosters or buy made ones - so go by the fit and make up of the nappy itself rather than the available inserts

HTH