This may be worth a shot:
Use a round piece of cork from the hobby store to put in between the two transducers. Then pressure fit the "sandwich" in your E side bridge wing like a conventional bridge wing pickup.
You may need to file the bridge wing surfaces parallel to each other to get a nice and square fit. Get the pickup in there good and snug, but not so tight you can't easily remove it with your fingers. Piezos need pressure to sound their best.
You could also use some hardwood veneer from the hobby shop to make the sandwich once you get the fit and measurements you need. After testing and adjusting the fit you could superglue the pickup sandwich together (but not to the bridge of course!)
You could also try just using each pickup individually on one or both sides of the bridge and shim them in.
Do plenty of experimentation before making anything permanent.
I cut small squares of self-adhesive maple veneer and attached them inside my bridge wing to shim my Underwood and it worked perfectly. I can now remove the pickup without disturbing the fit.
This may or may not work, but it's worth a try! Anything will sound better than that pickup fit the stock way!
Just an idea, and I have heard of other guys doing a similar thing, supposedly with good results.