The Silver Scroll winners are touring Europe to promote their newest album, Straight Line Was a Lie.
The tour will then make its way to North America with shows scheduled across the US and Canada in late October, November and December.
The band said anyone who sees the instruments show up for sale or has any tips should contact them.
They are not the only Kiwi band to be robbed in France this year.
Death metal outfit Organectomy had gear, money and passports stolen after a show in Lyon in May.
After driving north to Audincourt, the van was parked at 1.30am, but when they awoke, their bags were gone, drummer and driver Levi Sheehan told the Herald.
Thanks to support from the community, the band were able to keep the tour going.