Been using two of the Hafny style mirrors on my cargo bike for the last couple of years (sold as 'Klevsour' but arrived branded and boxed as Hafny). They don't wobble, stay where you position them and have a wide enough field-of-view to get a decent idea of what's happening behind you. Having the left-hand-side mirror as well is definitely useful in busy traffic and on roundabouts and multi-lane one-way systems; helpful for checking he trailer is still attached too
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I tried those, they showed me clear non-shaky views of my elbows. I have 580mm handlebars - wider would have worked out better.