Looking for small, high quality, high output audio transducer for

I have a motorcycle intercom system with helmets that have had
microphone and speakers installed.

The intercom system is of high quality, but the speaker transducers
that are provided are not able to product adequate volume without
distortion.  The problem is that I wear ear plugs while riding, so the
transducers must produce pretty substantial volume for their size.

So I am looking for a transducer that is able to produce good quality
sound (also want to listen to music)at relatively high volume levels.
I suspect that something like what I am after will be found in a set
of headphones, but I doubt that any retailer is going to be very
cooperative about letting me tear apart headphones until I find a set
that contains a transducer that will work...

I think the ideal transducer woud be in the range of 40mm diameter,
thin, with the diaphragm protected on the "front" side from direct
contact.  DigiKey and Mouser show some things that may work, but I
thought I'd ask here before I started just buying & trying...  Any
thoughts?

Thx
Scott Kelley