Top of my head I can't remember the company. I will post it up tomorrow if I get chance. They do the job to order. They already did the clowns on the bandit fighter 2 (there were two versions of the clowns and I obviously chose the one I liked, well, the other half had input too, which was surprising as she hates clowns). Process was choose helmet and specify design, pay the guy and wait four to six weeks for it to be done. Cost is based on what you want and any extra work.
moving on, the bandit fighter 2 is street legal if memory serves (and cheaper than mine, but with a larger visor area). There was nothing to stop a buyer designing their own for him to do, but I really liked the clown I got, so job done. The back of the helmet is also personalised with some other flashy artwork rather than just being a totally white helmet. The only reason I haven't shown the back is because I want to keep mine unique to me while breaking up the sea of white. It would have worked fine just as a clown, but I wanted more.
I was already taking a bit of a gamble in having the job done on an XXR as it wasn't the usual target for the clown face. He did a good job though so no complaints.
The actual bare helmets are here for anyone wanting more info on shapes and styles (and legalities for countries and states etc). http://www.bandithelmets.co.uk/