The A would be a solo-tuning G string.
For the E, indeed, that's a problem.
You may try to get in touch with Super-Sensitive, they've made special strings for the Violon Octet.
Also the Bass Viola de Gamba's highest string is a D.
Maybe a light gauge one could be tuned up to E.
Don't know what's the scale they're made for exactly, though.
Ce message provient du Québec! :)