Health store, online
You can buy this at most health food stores or, of course, online.
There are 2 forms of Niacin
that do not cause flushing. One is time-released niacin. However, this form has an increased risk of elevating liver enzymes, so if taking one should get blood tests of liver function periodically. Inositol hexanicotinate is called no-flush Niacin & is safer but may not work as well- see my comment:.