If that won't work then you could clip it to the waist band of your pants at 4 O'clock in the waist band like a knife. But it'll seem really odd for a normal pen to be there and a tactical pen will look like a tool intended to be used as a weapon worn in that fashion.
But in general why is your pen falling out? I don't think I ever had this problem when I used to carry pen in my pocket.(for geeky reasons, not defensive reasons)
In your pocket, or purse if you are a lady. You can clip it on the top of your boots if you are wearing boots so the pen is inside your boots. But remember that if you re attacked you will still have to get to it so you carry it where it is most convenient for you. If you are walking at night I would simply carry it in my hand. Be careful if you have to use it as it could be considered a weapon. Anything you carry with the intend on using as a weapon even if it is a pen (which is normally not a weapon) made to be a weapon like a tactical pen it can land you in trouble with the law.
I use a regular pen clipped to the collar of my T-shirt. It's not exactly concealed but it is inconspicuous all the same. It is easily accessible, and doesn't take much effort at all to grasp and brandish when necessary.
A pen is not an ideal defensive weapon if you ask me. If an attacker is good enough in conflict, he may be able to avoid any strikes, even knife ones. If you want a good self-defensive tool, you can buy a pepper spray. Those are not that easily avoided by natural instincts that come through millions of years of evolution. Think about it.
I doubt that someone with no skills and experiences, can actually that easily stop with a striking tool, an attacker that is good in conflict, while everyone can pepper spray right?. Most of people that I know and have a lot of successful experiences, got barely hit in most of them. So an attacker that is actually good in conflict, may read your reactions. A more realistic defensive tool, has to be something that people are not used to from evolution and that is a pepper spray.
I am not trying to scare you of or something, perhaps most attackers are horrible in conflicts, but a pepper spray is the tool for this.:)
Down your bra? It's been done before lol.
I recommend an ankle knife. Much more effective than a pen and it would seem much easier to conceal.
You need health care.
Back of your hand, shirt pocket if you have one, back pocket perhaps, sleeve, sock, or wear pants were the pen won't fall out of the pocket.
Your options are limited.
In your front shirt pocket.
in your pocket? lol this question is stupid
your sleeve
