I use these in my Variax 300 electric. I expect they will also fit the V600 but you may want to ask the manufacturer.

http://www.graphtech.com/product-41-2/

I own four Variax 300s, and over the past 6 years have gained some insight by tweaking, honing and modifying them with hopes of achieving optimum playability and sonic quality, thus bestowing each Variax with my own personal and reliable performance characteristics, however there are many things that can cause problems, so on occasion the piezo pickup very well might not be at fault. Many Variax owners might have (Vari-ing) degrees of intermittent problems that reside within the Variax's processor which is the( brain) control center (including It's internal memory) that can fail and manifest into a major flaw, and for some a complete and disastrous breakdown. When Variax 300 & 600 trouble occurred while the Variax was under warranty, the Variax was returned to the place of purchase and if the problem could not be determined and resolved, the Line 6 solution was just to replace the Variax rather than back-piling a load of extra work on the Variax technicians who were focused on Variax 700 repairs. After the 300 & 600 warranties had expired and owners needed repair work pertaining to the electronics etc., they found out that qualified Line 6 repair centers wanted $150 + just to look it over, so many owners thought it over and were reluctant about coughing up that much dough to just take a peek and considered buying a new Variax , especially 300 owners. I have heard of and read posts about piezo swopping, many with good results (the GraphTech name being tossed around quite a bit). LIke I mentioned, there are many possible culprits. Some Variax 300 owners might want to read my posted document titled: Variax 300 (bridge problems) solutions at the (Variax Guitars) & (Variax 300 Endangered Species Consortium) Community Groups.