That is a fairly personal sort of a problem to answer as you have already suggested alternative type moulded ear plugs.
Not sure how experienced you are so I apologize if I oversimplify anything.
But helmuts do make a big difference, some are a lot noisier than others often as you have stated the visor shape and the way it fits affects noise.
Changing helmuts may not solve your problem though.
I would suggest the moulded earplugs will be the way to go, experimenting with Lids is sort of expensive!
I currently use a Suomy helmut and I would say noise is average, but I am a bit hard of hearing and like noisey pipes and do not like using ear plugs (no doubt a contributing factor of my hearing).
cheers,
DaveM
