I am sure this must have been done before but blowed if I can find the topic.
I have worked out that I can get some 4" (10cm) speakers in the side trim panels of the Sportster. I quick troll on Ebay produced a load of results - some with brands I am familiar with in my status as an old git (pioneer, alpine etc.) but some I have never heard of before (vibe, boss etc.).
I don't want to spend a fortune as they could always get damp and wrecked - so, what represents good value nowadays - is it one of the old school boys or one of the new kids on the block?