Tiny house toilets: The Little House Company

 The Little House Company has been selling a range of urine separators/diverters, waterless composting toilets, and other accessories (including solar panel kits) since 2012 and is an official reseller for Kildwick and Separett compost toilets. Here's what co-owner Martin says about the business:
Our primary product range is waterless, urine-diverting composting toilets – these make a great difference compared to a regular toilet because they not only use no water (so you save precious drinking-quality water, and save the energy used to purify and transport it to you), but you’re also creating a useful product out of the ‘waste’, which would previously have been passed on to someone else to deal with.
The company also makes its own model, the Eco-Loo, which comes in two bespoke varieties, the   'Divert' (urine is diverted to a soakaway pit/external container) and and the 'Capture' (built in tank which can be completely self-contained). Clients include the owners of a straw bale roundhouse and Airstream Holidays on the Isle of Wight. There's an excellent FAQ on the site here.