If you have some luck of the devil then that maybe possible, but on the other hand, you may end up with nothing even doing 3 S convoy plunders for a month .. So, your statement "As example you can get one by doing so at 2 or maximum 3 plunders" is not precise and sure that it will happen ..

Anyways, regarding this query .. Plunder book is still implemented in this game, tho it drops really rare and just rare .. My experience, i can get 1 to 3 per month or 1 every 2 weeks ..