You can still buy Lambivac for your goats, it is not up to the merchant to decide what you use it for. If they won't - find another (if possible). Doses are the same as for sheep (i.e. two ml once for booster, but every six months rather than once a year as for sheep, and the initial course is 2 x 2ml 4 weeks apart). It is an injection under the skin, and with goats it works quite well if use the bare skin under their front leg (their arm pit in other words), just lift the skin up like a tent and inject into that. Best done with two people and goat safely restrained.
If not available through the merchants, your vet may have some doses around, but mine doesn't. But vet could order it for you. Smallest one you can buy is 25 doses pack unfortunately. There have been threads in the sheep section on how (if at all) you can store it.
People use Heptavac as well, but as far as I know goats don't suffer as much from the adult sheep clostridial diseases, so I am staying with Lambivac.
You will find that there are very, very few medicines actually licensed for goats, so your vet will advise on which sheep/cattle medicines (such as wormers - very important) you would be best to use. Withdrawal for milk is then usually a matter of "how long is a piece of string...", and it will be up to you to decide for example how long not to drink their milk.