Are you recording a super-paranoid act (like Bob Dylan or Tool)? Or just a standard touring band?
The problem with your lap is that it's going to sound awfully muffled down there. The people in front of you are blocking the sound.
The problem with a bag is that no matter how still you try to sit, it's going to crinkle.
Unless you've got some really anti-recording band playing, it would be worth it, as suggested above, to just put the DR-07 in a shirt pocket with its mics peeking out (so it doesn't rustle against your shirt fabric). Or in a little camera case around your neck--though the lower you go, the more muffled it will get. Try at home to see if you want to put something--soft uncrinkly plastic, a cloth, a paper towel--in your pocket or camera case to raise the mics into open air.
Everybody now is toting around cellphones, cameras, etc. Security guards pretty much ignore them unless they look like professional video or camera equipment--telephotos, shoulder rests, etc. There are a handful of bands that are maniacal about it, but I have taken my Sony PCM-M10, which also has its mics at the top, to dozens of concerts in a camera bag, and it goes right through. One guard just warned me not to use the flash. Oh, OK : )