Where can I find implants?
According to this answer to another Fallout New Vegas question, there are implants available for purchase which will increase SPECIAL stats or grant health regeneration and increased damage threshold.
Where can I find these bad boys?
Solution 1:
All non-dlc implants are at the New Vegas Medical Clinic. Right across the road from the Crimson Caravan Company, just a bit NE of Vegas Proper.