Personally, I wouldlnt drive around for too long, if at all, without them. Theyre designed to keep the engine block and tranny together, at the bottom. Yes, there are quite a few big-ass bolts holding it together most of the way around...but still. Honda put them there for a reason. Buy them.
Theyre actually under Alternator-Engine Stiffener (I know, because I looked under every catagory (bottom up......)).
Numbers 2 and 3
11950-P2J-000
11960-P2J-000
I suggest you get the bolts too.