I believe Fidelity offers a sweep into at least the SPAXX (FIDELITY GOVERNMENT MONEY MARKET (SPAXX) - 10 day yield 4.95%) and could be other even higher yielding MM's for accounts of far lower minimums. You should call up to confirm.
But I personally don't like the Fidelity site, but then I only use the fidelity basic platform since I use Think or Swim more at TDA.