Raising toilet height ideas

Has anyone found a way to raise the height of a toilet using aids/equipment? I have tried a Homecraft Savannah raised toilet seat but it didn't clamp onto the bowl firmly enough, lifting up on one side when my client transferred on/off. A grabrail on the wall is not enough.

An over-toilet frame is not suitable for my client, either.

You can get a "collar" that goes under the pan. This may require a new pan though....$$$
Search the ILC web site under "building"