There is no run-flat tire available for the i3. A run-flat tire would have a high rolling resistance and would be heavy, neither of which i3 designers would have approved.
Happy that an alignment solved your steering problem. Our new 2014 i3 had the same wandering at highway speeds and stiction at the straight ahead steering position, but I don't recall a lack of centering being noticeable. I never had its alignment checked, but there was no unusual tire wear, pulling to one side, etc. Our former 2019 and current 2021 i3's both track straight at highway speeds with no need for frequent corrections like in our 2014 i3, so I just assumed that the suspension changes that BMW made in later i3's might have solved the problem.
