If you want to go inexpensive, these nylon thumbscrews work well (I also use them in my PA rig), and you get a bag full of 'em in case they break on you:
Link Removed
If you'd rather go with stainless steel like I did for this application, grab 4 of these:
Link Removed
along with a bag of washers:
Link Removed
The steel units are perfect for this setup in that you can still easily turn them in the recessed confines of this cabinet, but they aren't cheap. Should last forever, tho.
How long should the screws be?

