You can buy Treasury bills straight from the government at TreasuryDirect.gov. The website is antiquated and clunky, but once you master it you can buy a new T-bill each month. That way, you’ll always have one maturing every 30 days, keeping you liquid and enabling you to earn more on the latest T-bills as rates rise. You can also arrange to reinvest the proceeds in new Treasury bills automatically as each one matures. [end quote]
Other possibilities for near-liquid include agency and high-rated corporate bonds of about 1 year maturity yielding 2%+ on the assumption the Fed will continue to raise rates for a while.
And, of course, I-Bonds.