I have physical copies available at conventions and plan on setting up the web store in the next month or so for my next book Out of Orbit as well as getting more copies of Battle School printed and listed there.
Hey! Sorry, yes the pre-orders have been closed for some time (though I failed to actually close it till I saw your message). I've been working with the team at Infinite Citadel (my publishing company that I started), and we're doing a rules update as well as a reprint for the game later this year. Keep an eye out!