You can find them at Michaels and at AC Moore (both are arts & crafts chains with several locations in the Boston area). They each have candy & cake making sections where you can get the candy foils/cups, molds, boxes, etc.
A C Moore Arts & Crafts Store
145 Middlesex Ave, Somerville, MA
Michael's Arts & Crafts
17 Mystic View Rd, Everett, MA