When we talk about the PAVN in this context, we need to keep in mind that they were the national army of North Vietnam and that units that fought in South Vietnam could and were equipped differently from units and other types of local forces stationed in North Vietnam.
With that said, the majority of the pictures we have of the PAVN wearing any sort of helmet, be it a Chinese one or a helmet from the Soviet bloc, are usually from units in North Vietnam. Some of the most famous photographs of this are of anti-aircraft batteries and the often local militia tasked to man them. Take this photograph as an example.
For PAVN soldiers actually fighting in South Vietnam, this would have been more uncommon. The iconic headgear for the PAVN was the sun helmet/pith helmet. This was issued to each and every soldier and used to protect the wearer from sun and rain. These helmets could be made of plastic, cardboard and even cork. Just like the PAVN uniforms, they could be found in various colors and shades of brown, khaki, green as well as the less common blue and white. The helmets could be worn with an insignia, but this was not common in the field. The helmet could be worn with a cover made out of cloth or a net which could be used to camouflage it. Beyond the field uniform, which was manufactured in North Vietnam, China and other countries in the Soviet bloc, the equipment worn by the PAVN was commonly Chinese in design. Rigs and other webgear that a PAVN soldier could wear depended much on the weapon that they carried. An SKS rifle would require a different equipment than an AK-47, but a good example of how it could look like is this photograph which depicts a khaki sun helmet, an AK-47 and its corresponding rig containing pouches meant to carry AK magazines. Just like the field uniforms, these were produced either locally or from China.