Fine, but you should have been more specific that you wanted to keep your Schwab tIRA and would not transfer money to another tIRA in your initial ask.
Given that, I don't have much of a better idea other than dipping into higher rated preferred stocks. Schwab has a pretty good preferred stocks screener that I use or some of their fixed income specialists might be able to put a portfolio together for you. I have 50 tickers that I've bought over the past 24 months and my investment grade holdings yield about 5.5%.
A few examples... CBKLP is rated BBB+ and yields 5.95%, GL-C is rated BBB+ and yields 6.09%, PUK.PR is rated BBB+ and yields 6.13%. If you do delve into these be sure look at call risk.
Or you could try investment-grade corporate bonds and let Schwab's bond desk build you a portfolio.
Or you could look at the muni bond target maturity funds like Bulletshares... a 5-year ladder with funds terminating in 2022-2026 would yield 1.6% and have a 3.57 duration. Or you could just buy the 2024 fund... BSMO... which is yielding 1.4% with a 3.36 duration.