If you are in California, there are tons of nurseries in your area that could order it in for you - you just have to ask.

I have gone to 5 of our best and largest nurseries nearby and everyone just tells me that they haven't heard of the Blue Moon variety and don't know where to order it from also. The last guy even told me "that sounds like something you would have to order from the East Coast" ....

I just did a google search and there are plenty of places that sell in the gallon size - I'd suggest you do your own search and just start calling nurseries that offer this plant, and ask if they can get it in the 5-gallon size and send it to you - I doubt they will, though.

I have already done my own searching for this wisteria. Yes, there are plenty of nursreries that sell them in a small one gallon or quart size container and I have called a number of them to see if they have a larger size. They don't; I found one place that has only 2 and I need a total of 4. This is why I came on hear just to ask if anyone else knows if there is a place that They know of that sells them around 4' tall; not so I can be told to just do my own research since that is what I have been doing. So if someone knows and can actually be of help, then please do answer this posting. Thank you.

Forestfarm has Blue Moon but not as big as you are looking for. Their plants are 1-2' but they are a reliable nursery with excellent customer feedback. I hate to say it but Wayside has one of the worst reputations of any online nursey. The plants from Forestfarm will be much nicer.
http://www.forestfarm.com/product.php?id=4897

The link below is to a nursery with 3 gallon pots of the Wisteria you desire. I have not ordered from them.

I have read how vigorous Blue Moon can be.

http://forums.gardenweb.com/forums/load/vines/msg0913585223346.html

Here is a link that might be useful: source of 3 gallon Blue Moon