We do not sell replacement parts for the Galileoscope. The most common complaint we receive is that the eyepiece lenses are missing from the kit. They’re not — they’re just easy to overlook. As noted in the assembly instructions, the lenses are packed in layers of white styrofoam inside a plastic bag tucked into the lens shade/dew cap.
The foam separates into two blocks, one thick, the other thin. The thick block holds the objective, a large lens wrapped in tissue. The thin, lighter block is secured by small pieces of transparent tape. If you carefully cut the tape on one side to separate the thin foam layers, you’ll find the six small eyepiece lenses nestled inside.
There are only four parts in the Galileoscope package that might wear out: the four O rings. The two small ones hold the two halves of the focuser tube together and are critical to the assembly and operation of the Galileoscope. The two large ones help hold the two halves of the main telescope tube together but are not really needed, as the lens shade/dew cap on the objective end and the small main-tube clamp ring on the eyepiece end are all you really need to hold the main tube together.
The O rings are standard-size parts that are available in most hardware stores for about 75 cents apiece. The small ones are 1/16-inch thick, with inner diameter (ID) 1-1/16 inches and outer diameter (OD) 1-3/16 inches. The large ones are 3/32-inch thick, with ID 1-5/16 inches and OD 1-1/2 inches. But, again, you don’t really need the large ones.
Another small part that some people overlook is the hex nut used to attach the Galileoscope to a standard photo tripod. This is a standard-size part (1/4-20) available in most hardware stores for less than 50 cents.