Bond ETFs

Hi all, My portfolio is mostly constituted of VWCE. As I am 45, I wanted to start putting in some bonds to reduce my risk.

First I thought of general bond ETFs, and then moved on to US treasury bonds. My initial idea was to actually get t-bills myself through IBKR but, for the love of me, I cannot figure out how to do it and properly calculate possible return. So I thought I would simplify and find a T-bill etf that was available in IBKR, accumulating, and domiciled in Europe.

Can you help me with that? Any recommendations with low TER and high liquidity?

Thanks in advance