Sugru putty might be a fix, but you paid £4. Good levers TBH. I had similar on my Fixie (but with the plastic trim). Even the old early 90's levers had the trim on levers upto 600/Ultergra - DA got polished alloy.
For £4 for immaculate lever's I'd let it go, and pop in something like Sugru to till in the top bit, or anyone got a 3d printer.....