I use a leash lock. It's not super-secure though. With enough time to enter the combo digits or with cable cutters someone could break it, but the idea is to make my board less easy to steal than yours.
Like this one:
I actually hate the lock itself because once in awhile the combo resets if I don't set it carefully. I came out of the bathroom and discovered that the combo I had set was no longer the one that would open it up. Shit! I started at 0-0-0 and worked my way up until i got the right digits. It only took about 20 minutes but it still was aggravating.
The small loop at the far end is also too small for the lock part to slide through, so I had to make a lasso type of thing. It's a dumb design, but at least it's always connected to the board without me needing to fill my pockets with anything extra.