Safest way to have cash available to buy

Is there a risk-free way to keep cash for crypto in the US?

-It doesn't seem like any exchange is fully FDIC insured with USD.

-Can't trust any stables in cold storage at the moment

-All exchanges that I'm aware of take several days for bank transfers to clear before sending coins off of exchange.

I would love to DCA at the moment but don't fully trust any exchange/stable.