QASM, or Quick Attach Surface Mount buckle is perhaps the most glorious invention on the field of buckles in this millennium. These lovely things integrate into the straps of most bags and into the PALS loops of the MOLLE system in a lovely way.
When it comes down to attaching something with a MOLLE buckle, the best solution are almost always buckles of this design. With the QASM buckles you can, for example, integrate a small bag as a part of tactical vests.
The weight of one pair of buckles (a female and a male member) is a bit under 20 grams.