I got several from NPD and, with the exception of one that had a broken contact (they replaced it at no charge), all worked well. I don't know who makes regulators today but there can't be too many manufacturers. The seller is the one you deal with and the best way to get any quality product is to install it promptly and if it's defective the seller will replace it, at least most will.
Jim
PS - flickering lights are often caused by poor grounds, at the lights, battery to engine, engine to car, etc.