I have a Stebel Nautalis on the DRZ and it is great. Had to separate the compressor from the horn as there is so little room on the DRZ to mount extra stuff up front. Horn is zip tied to the indicator and the blower is in the rear joined by some pressure hose. Works fine.

Don't know if anyone has tried these from DX.com - BikeHorn
Looks like a Stebel ripoff but at $US22.71 (= under $NZ30) might be worth a try.