I found it at underdogs: http://www.the-underdogs.info/game.php?id=5228
I regularly find old abandonware and public domain games there that are not obtainable easily anywhere else. So now I'll try to get it working under XP, @Corwin: you're on the way of becoming my go-to guy for advice on running old games on XP, that fits your avatar quite nicely :-) @dteowner: thanks, I'll check out the Heavens