Never had it, it's on my bucket list tho. From what I understand its almost impossible to find legally outside of Japan, and even in Japan you need a special fugu licence to sell it. So if you really do wanna try it, prolly gonna have to go to Japan.
You might be able to find it in the US (keep in mind it'll be fileted in Japan then frozen and flown over) but it is illegal to sell it at all in Canada.