http://rotocell.blogspot.com/#!
I know other such conversions exist, I meant I only made one. I did it because it was fun, though, so I don't mind that there are others.
I'd also love to have one. My friend here in Prague I think would be able to help with the design in order to keep the bell - it MUST be possible.
Also a Kickstarter could be great which I have experience in also. I will contact you :)