Fisheye

Hi,

I sold my 16mm pancake recently as I never used it. Then I have just been looking at some great fisheye pics and really wish I'd kept it.

So the obvious thing is to buy another 16mm pancake and a fisheye converter. I just wondered is the any other way of doing this? Can the converter be used on the 50mm prime (sorry if that's a stupid question), are there better options with other lenses, etc?

Thanks.