My source was Purple Taco, but that dried up last year. Trout Beads has a variety of sizes, including a large 14mm. I buy from him now and they are better than most out there, but they don't glow quite as long as the beads that Purple Taco used to carry. Hope this helps. Mike
Thanks HONDAM. I already have a GPSMAP 546 which I bought 2 years ago to have a separate chart plotter from a fishfinder. What I should have said in my reply was that I plan to get a Garmin Echo 550c to replace my old Garmin 300c.