How to join a local tour while in Tokyo?

I will be spending about 4 days in Tokyo and would like to go on a day trip to Mt Fuji. Any suggestion to join or buy a local tour package?

If you stay at a major hotel, you can pick up book a tour at a hotel reception.
If not, you can book a tour via a website like this.
Japanican: http://japanican.com/index.aspx

I would suggest picking Grayline Tours over Sunrise for Mt Fuji.

I've tried both tours and for the same price, Grayline visits an additional area which is the Owakudani Valley which was defintely the highlight of my tour as I don't live in a country where I can boil eggs in hot springs! And the cruise on the pirate ship is defintely much better than the cruise that Sunrise offers whichw as a mere 5mins ride in a 'normal' ferry.

Plus I've gone on the Sunrise Mt Fuji tours twice and the first was pretty good. But the second time which was earlier this year, Sunrise was obsessed with keeping to schedule. They had 5 buses doing the Mt Fuji tour that day and our tour guide had to frequently coordinatie with the other buses to make sure that all of us don't arrive at a particular place at the same time! So you can imagine we had to keep strictly to the time given and had to leave before the other buses arrive. So it was a really rushed and unpleasant tour.

Whereas Grayline allowed us extra time to linger at certain places if we requested for it and if conditions allowed for it.

http://www.jgl.co.jp/inbound/