Alternators

[flatchat(Chris)]

Although there are probably more petit Alts. available , this Daihatsu one is the smallest common cheapie I could find and measures 130mm o/a length from centre of pulley(poly v), it would fit through a 120mm dia hole. The terminal post is on the side as well.
Good luck any how.

 

[Rick]

Mitsubishi (brand) alternator is one of the smallest made. It is used by many of the import car manufacturers.

 

[Jack Houpe]

Ok this is a little off the wall but my kubota diesel lawn mower has a very small alternator. You may only get 40-50 amps out of it but its small. Here is picture.