A Time of War Companion has certain cosmetic cybernetic mods that would make it possible for a catgirl, such as the tail and retractable claws (some of these cybernetic mods have non-cosmetic versions of them as well).
There are also Cybernetic adaptation kits which are sets of removable implants which mimic a Naga, Centaur or Mermaid. These have availability ratings of F-F-F, so they're rare, but out there. Surprisingly there isn't a default catgirl kit.
ATOWC also has the mutation trait where the -3 value is defined as "Functional Tail and mobile ears."
So there are a couple of ways to do it, but there isn't a canon character that I know of, unless you count the artwork on page 188 of the ATOWC which shows a Pleasure Circus performer with a tail, ears and customized removable arms and legs.
Also, in FM:SLDF, (page 207) in the 108th Mechanized Division, its mentioned that "three soldiers of the 108th were discharged for receiving cybernetic animal ear implants in breach of SLDF uniform regulations."
So its not entirely unheard of...