I hear you, I don't think bonds are worth the risk, and cash is pretty much a guaranteed loser.
Trying to time the market (i.e. when the market goes down, I'll just put the rest of my money in) is rarely a good idea. If/when it goes down, are you going to have the courage to sink more in when the rest of your portfolio is down 20%? What if it drops lower? And when will bond rates normalize?
Anyway, some ideas:
You could add commodities to your portfolio, but this is usually hard/expensive to do with a fund.
You could add a position in gold (GLD). Typically it will offset a down move in markets.
You could buy TIPS (TIP).
You could go long bonds (TLT) and sell covered calls against it (requires some management).
You could go short bonds (TBT) and sell puts against it (requires some management).