I have the main parts of a DIY Kalk Reactor. It's two sections of 4" clear acrylic pipe, the 4" PVC pieces (2 end caps, a coupler to join the two sections of acrylic pipe, and the stand) I'm pretty sure I have the PVC pieces for the top too. If not, you can get them at Home Depot.
In addition, I have a complete set of printed instructions on how to make it.
I use one like it, but mine is about 40" tall...this one will be about 24" fully assembled.