The drug den is the best place for strange pills. Unfortunately you have to find so many pills to unlock the den first. However there was a fix that guarantees some pills starting out because it was hard for some people to get them.
You should have access to a bounty board in Medical that will give you targets - including a special target who is known to carry contraband. Track down the target (or force the encounter if they are sleeping) and attack/punish them to get the pill.
