The best options are Treasuries or CDs since they lock in rates for the term of the bond/CD. You should be able to do a little better than 5% though, I see brokered CDs at 5-5.5%, and t-bills are ~5.4% for 1-year.
RE risk tolerance, you really shouldn’t be doing anything risky with a timeline of 2 years. The potential gains will be absolutely dwarfed by your contributions, and any losses will delay your purchase date, especially if they happen at the end of the 2 years. 5-6% is pretty much the limit these days for risk free or low risk returns, so pick something and get to saving.