I think you have two options, depending of whether yiour bridge saddles are spec'd like some common brand bridges saddles (Hipshot, Wilkinson, ABM, Fender).
These options are:
- Graph Tech Ghost piezo saddles (
http://www.graphtech.com/products.html?SubCategoryID=19)
- RMC Pow'r Bass piezo saddles(
http://www.rmcpickup.com/products.html)
You'll probably need to measure the size of your saddles and ask both companies if their saddles are compatible with your bridge. And regarding Graph Tech, if you decide to buy theur products you're better of ordering from some company like Best Bass Gear, which sell cheaper than direct from Graph Tech.
Personnally I changed my whole bridge for a Hispshot fitted with GraphTech Ghost pisckups, bought from
www.bestbassgear.com (great service).
Hope this helps.