A common toilet is the Jabsco.

- Jabsco.jpg (22.21 KiB) Viewed 24996 times
They are probably the most inexpensive, but on two different boats I've had problems with them after about a year, and the kits for repair are quite expensive.
On the Ballad I installed a Raritan PHII which has given excellent service for three years so far. Individual parts and seals are less expensive, but I've yet to need any.

- Raritan PHII.jpg (8.12 KiB) Viewed 24996 times
On either unit the pump and handle can be easily switched to the opposite side.
That's my only experience with toilets
