You say two years, if not more. If you want 100% certainty that it's available, your only options are CDs and similar; you could also consider series I bonds, for example.
Otherwise, there are varying degrees of risk available to you. Decide how much you need the money to grow -- if that $26K is enough for the downpayment, then stick with safe options to at least gain something from it.
If you're willing to take some risk, but it's still short term, you could put it into a short-term bond index fund. But that entails the risk of loss of principal, which you seem to not want to risk (and I fully understand)