I was thinking of getting it sometime back as well... but I find it pretty pricy. A new set of IR-E20 + WC-E67 would be about $215 at CP. Yep... the P5100 is currently 35-123mm zoom (35mm equivalent), and with the wide angle adaptor, it would change it to about 24mm (35mm x 0.67). I tested out a 3rd party one at AP Funan, and it was bad (changes the color and had bad CA). I went to CP sometime back to test out the original Nikon one, and the results were very decent.
Sometime back, "appleture" was selling it, but I decided not to buy it in the end. You can check with him if he still has it or if he has sold it. I found him not very friendly when I was inquiring from him. If I recall, the last price that appleture offered to sell it for was $100.