The Kremona violin pickup is among our favorite value options for amplifying acoustic violins. The piezo element is enclosed inside a thin wafer of wood, and mounts in the wing slot of the bridge (see large picture for detail). Now comes with a 1/4" Carpenter jack sturdily attached to the instrument with two turnbuckles.
This pickup is easy to fit to your bridge, and even easier to remove when not needed. For the budget-conscious buyer, this is the least-expensive, most convenient way to go electric with the viola you've already got!