Your right 45Nut they only make the plain Ruger rings. If they made the Ruger rings in signature style they would sell like hotcakes!! Probable Ruger woun't let them.
If you do want to use the signature rings there are a couple of options. Burris sells a two piece adapter that coverts from Ruger to a weaver.
ADAPTER Or you can get a B-Square mount that goes from Ruger to weaver rail.
B-SQUARE MOUNT
Both mounts add weight to the gun. The B-Square mount is large and "clutters" up the lines of the gun. If Burris did offer the signature rings in the Ruger style mount that would make it look factory. To bad they don"t.