Jim:
I had the same thing happen on my BX22, although I was not in anything that I think could have caught the boot. I noticed the tear, but concluded that there must have been a small tear from new, and it just grew due to the wide angle swept by the joint. I replaced it myself, and the dealer swapped the part under warranty. Replacement was pretty easy, except for the narrow wrench you need to grab on the cylinder rod. I ended up grinding down an openend wrench to "thin" it to fit. Setting the toe-in was easy using the measurements in the owner's manual.
I did a little hunting for a replacement boot, but came up dry. I was thinking about trying to hunt down the manufacturer, but when the dealer said he would exchange it I gave up the hunt. But it might be good to find a supplier since they are held on with just a little wire clip.
I considered putting some of the cloth mesh that they have over the hydraulic hoses as a protective cover on the joint, using a couple of tie wraps to hold it in place. If I do find it gets torn I will most likely add the protection. Unfortunately they do hang out there with little protection.
Let's see if anyone else found a source.
Paul