• Vanguard Treasury Money Market Fund
• https://investor.vanguard.com/investment-products/mutual-funds/profile/vusxx
• expense ratio = 9 bps
• invests exclusively in Treasuries
• Interest from this fund is exempt from state and local taxes.

Ref:

• https://thefinancebuff.com/money-market-fund-high-yield-savings-account-guide.html#htoc-vanguard
• https://investor.vanguard.com/investment-products/mutual-funds/profile/vusxx

• the SPDR S&P Regional Banking etf
  • ticker: KRE

• https://github.com/KamarajuKusumanchi/market_data/blob/master/funds/expense_ratio.csv