Sources for full blood Japanese wagyu from Japan are very limited. Consumers are best advised to seek online marketplaces such as Amazon and eBay. Expect to pay very premium prices and high shipping rates.
American domestic sources for full blood wagyu do exist. Many have their own websites that can be Googled. Be aware that full blood wagyu may taste different from source to source.
The Japanese say that wagyu raised from grasses grown in volcanic soil and from pure water sources are the best. The Japanese in each growing region also tend to specialize their techniques in feeding their wagyu cattle everything from sake mash to olive branches. Thus every “brand” of full blood wagyu will have its own flavor profile.
Full blood wagyu that is American raised will reflect differences by location and feed, too. The grasses of Pennsylvania are quite different than the grasses of the American west. Consumers are advised to try wagyu from different locations to find a wagyu preference.