Spend $300 or whatever it cost and purchase a side bagger for your mower. A little gas money and a very small profit. Consider the hard work and extra labor time an investment for the next leaf job. It is paying for the new bagger. On the next job, and there will be more, you can charge more money and spend less time doing the work.
I personal mulch when I have grass, and rake (blower) or vac in dirt.