Are you looking to mount something that can only go on a weaver mount? If that's the case you could have it drilled and tapped. If you want to use a 1" scope on a rimfire base, Tasco sells bases with integral rings that fit rimfire grooves but have 1" rings.
There are many adapters that make it real easy. Here is an example:How can I modify a grooved scope receiver to a weaver mount.