What size adapter will fit a nikon p520?
What size adapter will fit a nikon p520?
There may be some 3rd party filter adapters that will fit, which consist of a sleeve with a thumbscrew attached to the side. Basically you slip the sleeve over the extended barrel and tighten down the thumbscrew so the sleeve does not fall off. They also have a filter thread on the end so you can attach a filter. You can find these on Amazon.
However, I strongly urge you not to use any of these sleeves. First, they can only be used for a filter, not an aux lens, as the lens is too heavy and likely to damage the delicate lens mechanism on your camera.
And if you forget to remove the sleeve before turning the camera off (or if a low battery shuts the camera off), the attached sleeve could damage the lens when it attempts to retract.
You have a superzoom on your camera already, and honestly, I can't see why that is not already plenty of lens. If you want a filter, which is a legitimate need, then I suggest buying a Cokin DigiShoe, which is an adapter which attaches to the camera's tripod socket and extends out over the lens so that you can use Cokin filters.