The new Savotta Askare hip belt works perfectly with Jaakari S. You could say the feature was intentional but strangely it is not advertised.
You can use Askare as an extra space and to get hip belt capability to the Jaakari S backpack. This works really well with heavier loads and while bicycling.
You will need two split bar female 25mm pals mount buckles (or two G hooks) and either a small piece of 25mm /1" webbing strap and two G hooks
or a small piece of elastic cord and one toggle.
With the buckles + g hooks it takes about 6 seconds to attach or remove the Askare from the Jaakari S backpack.