Amazon.com : 3X Barlow Lens, 3X Astronomical Telescope Eyepieces Barlow Lens with M42x0.75mm Thread, T Ring Adapter for 24.5mm Astronomical Telescope/Digital Camera : Electronics
Barlow Lens | Shop 3x & 2x Barlow Lenses for Your Telescope - High Point Scientific
APM Telescopes. Skywatcher 3x Barlow Lens 1.25" with 4 lens elements