you can use dynamic shop npc https://rathena.org/board/topic/75400-dynamic-quest-npc/ just edit
setarray .Shops$[1],"Headgears"; <----- this
// set .Shops$,"n/a";
// Add(<shop number>,<reward ID>,<reward amount>,<Zeny cost>,<point cost>,
// <required item ID>,<required item amount>{,...});
// Shop number corresponds with order above (default is 1).
// Note: Do NOT use a reward item more than once!
Add(1,30001,1,0,0,948,300,950,250,931,250,998,250,607,50); <--- and this