Elecraft User Group:
The MFJ-281 Clear Tone Speaker work's excellent with the K2's and K1's.
I have 3 of them on 3 different radios. Inside they use a good grade 3
inch Mylar cone speaker.. They have a frequency range of 600 to 4000Hz
and they only cost $13 each. They sound great ! (I have no affiliation
with MFJ)
Donnie / WA9TGT