The starship is a bit retro, so the crew should also be a bit retro. Hydra Miniatures makes a great line of figures that would be perfect, if they were 15mm. This calls for a bit of conversion. The guys publishing Laserburn figures make some great sort-of-Judge-Dreddish-but-not-really sorts that have the right shoulder pads and skin tight suits, but they all have riot helmets on, too. The guys over at 15mm.co.uk also make a host of other 15mm figures with heads practically begging for re-assignment.
Every figure here is based on the Law Officers range, with heads donated from various other lines. The third guy and fifth guy from the left are unconverted. The head on the far right is taken from a fantasy archer figure, and the alien head is from the HOF line of figures.