My friend, MD in Tokyo, who is also Iaido 5th. dan kenshi, once told me, that in the old days there were many repair/service Kiseru shops (some mobile) in Tokyo. They were as popular as todays shoe repair shops, they were everywhere.
You just left your Kiseru for few minutes in the hands of skilled craftsman and he would replace the "rau" and service the gankubi part if necessary for a small amount of money.

Tobacco:
There are two brands available in Japan,
Koiki (小 粋) finely chopped, and Takarabune (宝船) not as fine.

Koiki kizami, is probably the most popular Kiseru tobacco today.
It is Japans original tobacco, cultivated mainly in the Tohoku region (North Japan). Chopped extremely finely, making the Kiseru smoking unforgettable, one of a kind experience!
As far as I know, Koiki Kizami is a product highly regulated by the government, buying it outside Japan is extremely difficult.
The only way to obtain it is to buy it when visiting Japan or asking a friend to do so... The quantity that is allowed to bring back from a trip to Japan may depend on local regulations.