The #5 drive's closest relative is the TRS drive, with some #6 influence.
Jassman and f311sr1 would be good folks to poll on their thoughts for average use on #5 drives.
I do believe that www.bammarine.com can get you parts for them.
Jassman (Jeff) had them on one of his 43 Nortechs.
f311sr1 (Joe) has them on his 43 Black Thunder.