Not to take anything away from the vendors, but if you're into do-it-yourself projects you should check out the <a href="https://www.info-central.org/support_clipwhip.shtml">clip-whip</a> article at <a href="https://www.info-central.org/support_clipwhip.shtml">Info Central</a>.
I made mine with the materials suggested in this article. For a more professional look and for color matching (as if red/black wires weren't enough), you could add heat shrink where the wire is soldered to the flat alligator clip.
Or, save yourself the trouble and order from a vendor on TRF.
In the testing I did with soldering vs. crimp the soldered cables kept the same Ohm reading after each use. The crimped ones started getting higher ohm readings after each launch. I think this was due to the oxidation from the hot gases as the motor lights.