Onguard mini u lock. $30 and you have to cut both sides to get it off, both shackles are locked in. Small enough to prevent jacks from gaining purchase, light enough to carry around in a rear pocket or a purse. You can even buy little fabric sleeves on Etsy that hold it on your pant belt. Any mini u lock that has both shackles locked in would probably be fine. Don't get the ones that only lock one side inside the barrel. And take your computer with you, slip it in your pocket or jacket; almost all of them have a little quick release button.