I don't think so, as SL have gone under - my experience of these is to dump it and buy a moden toilet like a Jabsco - incidently I see XM Yachting are doing a toilet for about £70 now.
the remaining stock has been acquired by Yacht Parts Plymouth.
simple stuff like overhaul kits and diaphragms can still be found in chandleries.
i bought a complete pump unit last autumn, they told me there were 4 more left in the world after that. guess we'll have to think about an alternative make soon but i've never seen another unit that would fit in the space, especially close to the hull side.