There are several transformatives that can give you four legs; off the top of my head, they include (but might not be limited to) Catnip, Taurico Venidae and the Leitha Charm Necklace. However, most other transformatives will typically set your leg count to 2 before changing your leg type, while these add legs after changing your leg type, so you may have difficulty getting the specific leg type you want on your taur, assuming it's even possible.
Unless by "quadruped" you mean "four legs and no arms", in which case you're SOL. Steele will always have exactly two arms - having more arms has been repeatedly discussed and shot down due to how much effort it would take to re-write all the scenes in the game to accommodate that, and fewer arms would be even more work (for reasons which should be obvious).