I have achieved permanent nipple growh, both in length and diameter using suction teats called Supple Nipps.
These are made of silicone rubber. You lube them up, squeeze them onto your nipples and they latch on to you.
They are uncomfortable at first, but if you persevere and work up to the larger sizes, they do work.
You will need a bra, both for modesty and to prevent a disaster if one slips off!
The larger sizes do jiggle you about, so I wear a bra with a bigger cup size, pad the under cup with tissue, then rest my pumped out nipples on the padding for suppport. I can then wear them all day.