Ultra short USD bonds

I am moving from T212 (awaiting ISA to transfer to InvestEngine).

I am looking for ultra short governemnt bonds, to work like a money market. In T212, I was using iShares Treasury Bond 0-1yr about but cannot find similar on IE; all gov bonds start at 1 year +. I was investing in USD bonds because gilts do not offer less than 1 year.

Unless anyone has a better idea, I will try TIPS (iShares TIPS about).

Purpose: to provide between 10-20% of portfolio for expenses above emergency fund (kept in cash at the bank). This will only exist in my ISA, not pension.

Why not just use either of the two MMFs already available on the platform?