RallyArmor do not have a focus specific black flap with white lettering, the only focus specific offering with white lettering is on the red flap. They do sell a universal black flap with white lettering however.
RokBlokz may get my business because they offer the black/white combo, they are also known to be more rigid than the RallyArmor flaps.
From pictures I've seen I don't see why they would have to make any changes for the RS from the ST flaps, perhaps length, but then I'm assuming their short version would work just fine.. I guess I'll wait, but RokBlokz has a 5% off coupon going for memorial day (not sure how long its good for) "MD2016" and I'm awfully tempted to pull the trigger lol