There is no reason to assume that winglets have symmetrical airfoils -- in this case or in general.
Furthermore, the wing is likely twisted, and the winglet likely also has twist that manifests as toe-in or toe-out.
Generally speaking, very few aircraft have sufficient information published in order to perform a high quality aerodynamic analysis.
At the same time, it is great to learn about how sensitive the wing's performance is to these different parameters. You might try starting with symmetrical winglet airfoils and zero toe-in/out. Look at the lift distribution and compare to an elliptical distribution.
Then, add some toe-in/out and see what changes.
You should be able to achieve the same effects using either twist or camber of the winglet. So for simplicity, I would use a symmetrical foil and conduct an early study just changing twist.