My idea and your idea of "low risk" and "high return" may not be the same. But I'll take a stab anyway.
For surplus cash that needs to be 'safe', 'liquid', and 'performing', I like closed end municipal bond funds. I'm in IIM, IQI, NEA, and NIO. I earn a little better than 6%, tax exempt, on the average across the positions. I also hold some JPS which is a closed end fund invested in preferred shares. Yields 7.8% at today's price. I got in a little better and earn a little over 8% on my shares so maybe try a stink bid good till canceled order to see if you can catch a break.
My focus here is more on the "safe" than "high return" so YMMV.