Amazon offers its Amazon Prime members the LensPEN Lens Cleaning System, model no. LP-1, for $5.52 with free shipping. (Non-members can spend $25 or more for free shipping; otherwise it adds $5.58.) That's the lowest total price we could find by $3. This pen is lenses on cameras, camcorders, binoculars, and more.

Amazon Prime membership is $79 per year; however, Prime is free for college students for one year, and free for parents and caregivers for three months.