There are a few different sizes and styles used....if you like the kind that is typically used to hold fiberglass on that has a two hole flange that attaches to the panel (usually people use screws of rivets to hold the button to the panel) those are called "spring loaded dzus buttons". This style comes in either .500 or .550 long. Typically you use the .550 long for fiberglass. The other style Dzus, the botton actually falls off and you can lose them (these are used for interior panels but I have seen people who use them for fiberglass as well, these have a reach of .500) There are springs and plates to match each style.
There are "Large head Dzus Buttons" too and these are the ones I would use because they are a bit larger and the screwdriver or dzus wrench wont slip out of the slot as easily. They also make "Butterfly Dzus Buttons" that dont require a wrench but this style is not available in large head type.
You can buy them locally in Fife at a company called Art Morrison Enterprises (253) 922-7188 or (800) 929-7188. They are a street rod/classic car chassis builder and carry alot of cool stuff. Here is the link...
http://artmorrison.com/catalog.phpGo there download the catalog an go to page 56
Good Luck,
Steve