EPISODE I: THE PHANTOM MENACE
The helmet appears to be custom made, more info may be available as details of the film are released.
The belt buckle is a standard black plastic side-release buckle for 2" wide straps. Almost identical models are commonly available from REI stores which sell outdoor recreation equipment. The buckle was decorated with a gold Naboo Security Crest.
Clips are worn on the belt that a "knob" on miscellaneous props slide into such as the Security S-5 Blaster. By design, the props remain free to pivot within the clips and are released simply by pressing the two arms on either side of the clip. These clips are from Covertec a European manufacturer of protective cases for PDAs, HPCs, mini-notebooks and cellular phones as can be seen in the photos below.
Covertec Belt Clip
Covertec Cobra PDA Case and Clip
Security S-5 Blaster
Battle Droid Blaster