I have repens, but I am not willing to ship it in this weather. Where are you located? I am in central Michigan and looking for an excuse for a short drive.
As for 10-20 stems, how many tanks are you filling? I have Repens in one of my 55s and 5 stems have taken over half the tank quite literally. My leaves are quarter size (good food and good light). If you are talking about that store bought stuff, yes you probably need 10-20 for a 10-gallon. I can tell you where in eastern Michigan.