Hi there was a ridgid  clay cutter on trade me for around $ 800 a couple of weeks ago worth checking expired listings.

I use one that was originally designed for cutting cast iron pipe works  great on clay but hard to get into tight places as its  about 4 feet long. dont rotate to cut just set the chain untill tight on the pipe and squeeze a bit tighter and ' ping' your done, got to be careful as the edges are as sharp as broken glass!

the cheap dry cutting diamond blades they sell at mitre 10 on a angle grinder work well just need a R.C.D and no guard on the grinder.

Might be worth searching for cast iron pipe cutter.