Last one I saw simply cut the bottom of a 5 gallon bucket on an angle and set it in the front third of a 5 gallon bucket, I believe they held it there with a couple screws and installed a drain tube to a collection bottle.
I purchased a diverter from compoosttoilets.com (yes two "oo") which is based in the UK. Their shopping cart page doesn't allow ordering for shipment to the USA so they have an eBay site where you can order. They were very helpful answering questions and it was no problem getting it delivered to the US. They have several options available. I purchased just the diverter and made a nice composting toilet.