The Universal Round-Range Rectify Series drop-in speaker systems come in a selection of circular sizes. You can use these for applications that I do not offer a specific design for.
 
The speakers come fully assembled and tested.
 
Dimensions are:
UFIT-27D9-RC1: 27mmDia x 9mmH
UFIT-27D2-RC1: 27mmDia x 12mmH
UFIT-27D5-RC1: 27mmDia x 15mmH
UFIT-27D8-RC1: 27mmDia x 18mmH
UFIT-30D9-RC1: 30mmDia x 9mmH
UFIT-30D2-RC1: 30mmDia x 12mmH
UFIT-30D5-RC1: 30mmDia x 15mmH
UFIT-30D8-RC1: 30mmDia x 18mmH