I've seen various Waterpik and Interplak cordless models. You probably could
fit a nasal irrigator tip on them. Waterpik does sell a nasal irrigator tip,
which should fit on the Waterpik irrigator.

All those cordless models have very small water tanks, however.

Of course, you could also use a non-electric option, like a squeeze bottle
(Neilmed, etc.) or a neti pot.