Your local apothecary may carry it. For example, Merz Apothecary at the Macy's in downtown Chicago carries the entire line of Tabac. Although they have currently sold out of the soap in the bowl, they do have the soap refills.
Fragrencnet.com had the lowest price on the soap in the bowl and the refill also the price for the aftershave and the shower soap is the lowest around shipping is only $5.95, and took only 3 days. Shavemac lists Tabac on its site at prices higher than that.
I bought Tabac soap on Amazon for $15 and free shipping. Well, you would actually need to find some other item for $10 or more to qualify for Free Shipping.