Get the heaviest bar end weights you can find, the ones that are external to the bar. Look at what comes on a stock DR650. If you're not riding tight single track and don't need barkbusters, there are a few companies that make massive bar end weights for sportbikes that might fit your 690.

I've been fighting this problem for years with almost every bike I've owned up until 2017. I even designed and fabricated some bar ends with integral handguards that worked great.

These also look good although I have not tried them -