You could try star citizen...(idk if this pic works) look at their ships:
Also depends which alternative you reffer. 2016 game is different from the 2021 and 2010-2012 from the 2006-2010 version(the original DO, without those retarded skills set pilot sheet and thick lasers)
finding an alternative akin to 2006-2010 is unlikely. Since most of the game devs jumped on the liquid graphics bandwagon which looks like ****, and this is why darkorbit has ships looking like toys for children instead like real spaceships with shades and all it needs.
Warpfire was pretty similar too, though it stopped existing, and I don't know who holds or saved their CMS pages or at least have them in a html. or the swf resources. finding warpfire .swfs is as hard as finding deepolis resources. It would be better if they'd host somewhere on the github. but some probably if they re greedy they will ask a price for it...