It's presentation. I have a set of go bowls. The proper round 'sphereoid' type.
The two plastic squarish bowls (black and gray) are the only ones I've commonly seen in the US. Any others will likely cost much more than the wood bowls available at Amazon.
- HDPE widemouth plastic jars. They'll be cylindrical not spheroid.
- Use a food container (I've used ziplock small square 20oz).
- 3d printing: saw them being printed at 2012 Go Congress.
If you want pre-made alternate materials, search for 20oz or 600ml containers.