The Golem deck works pretty well against rainbows. I win most of the time, unless I get bad draws. And anyways, I don't have the money to switch to another deck right now.
If I really can't get two Stilettos before my fight, there is one thing I can do. Right now I'm using my main account, Dawn_Breaker, with all the upped cards and rares. I have a secondary account, Blood_Shadow, that have not picked its free rare weapon yet. I could grind that account to 500 score and choose Stiletto as its free rare, so that I'll at least have one Stiletto. If I have to do that, then I'll need to remove a Stiletto and a Bone Pillar to make the deck 36 cards and 50% Darkness.