Lacerta 30 cm Dew Heater Strip is 3 cm wide and compatible with tubes of 100-130 mm diameter. It requires 5V from a USB power source, preferably operated from a power bank.
Anyone who has observed in the autumn-winter cold knows how problematic dew can be. A dew shield offers some protection, but this is the "real" solution. Dew heaters are small heating pads or wires that keep optics warm. They can be attached around the eyepiece or tube using Velcro straps. Highly recommended for Schmidt and Maksutov-Cassegrain telescopes, where the corrector lens is particularly prone to dew, but also beneficial for refractor telescope owners.
The dew heater should not be operated from a computer as it may cause damage!