I- there are no words for how much I approve of this design. These designs. Not that you need my approval, of course. But still. Wow. I think we can tell everyone else they can stop searching now - we have found male Astrid. As for names - maybe Astrider? I looked it up, and apparently 'Astrid' is derived from the older name 'Astridr,' which roughly translates to 'beautiful/beloved god.' Which, really, really suits this design.
Actually, now that I think of it, the movies probably wouldn't be all that different if the all characters were gender swapped. They really did a good job of keeping things fairly even in terms of how each gender is portrayed.