Kevin,
Good question. I think I have nine of them that I bought from Bob Morrison last year, but I don't see them on his website either. They are wonderful heads and I hope they are still being made, although the nine I have will last a very long time. The only reason for replacing them would be if they got lost, because you practically cannot destroy one. It may be that their durability and cost have created a low purchase rate. The new broadheads that Bob is carrying look similar and cost less, but they cannot be as nice as the 300 Xtreems in quality -- not to say that they won't kill game just as dead.
I think the best way to find out if the Xtreems are still available is to call or email Bob and ask. I bet he would know.
Allan