A handful of stocks are carrying the S&P 500 higher, but opportunities exist at the smaller end of the market too.The benchmark S&P 500 index is up 15% this year already, but most of its gains can be attributed to the performance of a small group of trillion-dollar titans like Nvidia, Microsoft, and Apple. In fact, many stocks at the smaller end of the market are actually trading down year to date. That includes software providers like Workiva (WK -3.15%) and Bill.com (BILL -3.43%), which have seen lacklust ...