Whichever one you can find! Good luck with that. I've had my eye out for both of those knives for a while and haven't seen anything lately. From what I gather, several others are doing the same, so you'll have some competition. Whenever one pops up on the exchange, which is rare, it gets snapped up in a hurry.
It's easier to score full-blown Busse's than it is to find Swamp Rat or Scrapyard blades nowadays.