Your not going to find it published or on any offical website,
The orginization that tracks this information is called the AEM (Association of Equipment Manufacturers). The companies pay big $$ to the AEM to get sales data nationaly and on a local level. If your in the business, you hear bits pieces of this info all the time as its how dealership performance is measured. I guess the most concrete piece of information out there was at the last Kubota dealer meeting where they stated infront of about 5000 people that they now have over a 50% market share according to the AEM... thats about as objective as your going to get with these kind of claims. No, its not on a website, and no you can't link to the source. Take it for what you will.
Sorry, if someone wants to believe in something that they are told, whether for purely motivational (sales meeting) reasons or something else, it is sad that it's objective enough for them. Personally, I believe in seeing cold, hard facts. Quantifiable numbers, and if these numbers can not be published, or released to those who "pay big $$", than I'll bet the farm that they just don't exist.