Yeah, Tasca has pretty much the Cadillac of Sherman kits. They seem to only run each kit for a certain time though and if it's out-of-production at the moment they can be a little hard to find (at least for me). HobbyLink Japan generally has the in-production kits available. Other than that you can look at model shows and there's always Ebay, some dealers charge outrageous prices- esp check the shipping and handling before you bid. I picked up the M4A3E2 'Jumbo' recently for a very reasonable price so it bears checking though.

BTW: They recently changed their name to 'Asuka Model' so you might find them listed under that name too. 

The US distributor is Pacific Coast Models (who also sell directly -- cf their website).  If speed isn't an issue, luckymodel.com in HK is a good source (although they are low/out of stock b/c they just had a huge January sale that depleted them).  HobbyEasy.com out of HK is also another source.

Thanks for the advice Roy, and thanks for bringing this up S2B. I didn't know about Pacific Coast Models and didn't even think of using a Chinese company to look for a Japanese product. Just assumed Hobby Link Japan would be the best source...

If Tasca shermans are so well regarded, why in the world is Tasca not producing them any longer?

They were bought out by a new group, Asuka.  Some previously labelled Tasca items have come out under the Asuka label.  Other lines haven't come out yet.  The molds are extremely valuable -- no one is just going to sit on them.  Why the lack of current production?  Probably behind the scenes business issues.  I bet if you called Pac Coast models, their US distributor (and their own webstore), you might get the latest answers.