Hi, there is nothing wrong with nursing, provided your partner isn't near or menopausal when it could cause problems. Nursing for an adult is a little difficult as we can no longer latch onto the teat properly as this ends at around age 11, but practising with one of the newer breats shaped teats on a bay bottle will help. If your wife/partner has been recently lactating then she may well start up again with just you nursing at her breast. most women can be made to lactate just by paying a lot of attention to their breasts, fondle them, suck them etc. If your wife has another baby then you should start nursing as soon as the baby stops, this will help keep her milk production up.
I don't recommend going down the medication route. Firstly no Doctor will prescribe anything without a medical need. that leaves you with the so called internet doctors, but you will never be sure if you are being given the correct medicine or a fake, the medications also affect the woman hormones and cycle.