Ernie Ball (Greg) will have to tell what the deal is with their stuff. There are a few other options if it's a change in sound your looking for. Bartonlini, Seymour Duncan/Basslines, MEC and Aguilar all make good preamps. Try visiting their web sites to figure out what they've got and how to obtain in it depending on where you live.
It is possible to purchase Music Man electronics, as long as they are replacements for old or defective parts. We need the old parts sent back before the new ones can be shipped.