We used Cold Steel's training bowies and other hard rubber training knives for years, and after several rounds of begging, Lynn Thompson of Cold Steel made rondels for us.
The blade offers a high level of flex near the tip while remaining strong near the hand. Most HEMA rondel techniques work great. A few techniques that require stiffness along the whole blade will not, but that's the trade-off for having the safety of the flex.
Some people find the decorative points on the hilt to be a little scratchy (the wooden prototype had rounded points but this got simplified in the computer model for the mold). One minute with a file will soften these a lot though.