The cooling kits sold by yourmacstore were from Spirica:

http://www.spirica.jp/products/macitems/wck_md/index.html

Yourmacstore was the only US source for Spirica stuff but I guess they stopped selling the cooling kits. However, you can order directly from Spirica but you first have to contact a particular Spirica employee by email first. I believe there are details on how to do this on the cubeowner.com forum.

The AquaMac site, http://www.s155158671.websitehome.co.uk/watercoolyourmdd.html is also a great site for watercooling info for the MDD.