hi Owen,
I would suggest something like
http://www.bintel.com.au/Mounts---Tr...oductview.aspx
It can handle the weight and is belt driven (smooth and less backlash). they can track the night sky or at solar / lunar or other planetary rates.
Not sure what kind of adapters you will need to mount it but it should be achievable.
I hope that helps,
Cheers
Rusty