tko (dpreview, Panasonic forum, 20 March 2004) comments on possible purchase options (but had not actually purchased the lenses below at time of posting)...
Sony VCL-HGD0758 -- very good, very, very heavy (Weight: Approx. 690g (24oz), expensive ($200). I liked this lens but it's just too heavy for me so I passed.
Raynox HD-7000 -- almost as good as the Sony, cheaper and half the weight. The review site mentioned you could leave it on all the time with no loss of image quality. About $140...
Raynox DCR-720 -- inexpensive and light, on line photos look just as good as the big guys. Maybe not as fast? This would be a good lens to carry all day long. Cheap, maybe $60...CK's Digital Camera Page -- in the FZ10 section, amongst other useful information, are comparison of various wide-angle lenses (Minolta ACW-100, Olympus WCON-08B, WCON-07) and fish-eye converters.