What’s your favourite Campari substitute for use in a Negroni?

I have Martini Vibrante and CleanR gin, and tried combining these two to make an alcohol free negroni. It was ok but more fruity/orangey and lacked that bitter edge even though I used Angostura orange bitters.

I think Campari is the missing link? What would you recommend I add into the mix to give it that bitterness/herbiness edge that an alcoholic negroni has? Bonus points for brands that are readily available in the UK!

Many thanks in advance!