To bond metal to metal, soldering is an option if you know what you're doing, but perhaps not the most practical. The easiest — and cheapest — way to go about it is to affix a large safety pin to a wire barrette backing (found at most craft supply stores) using Krazy Glue ($3). Clamp to set, and then go make some for friends, do "The Safety (pin) Dance," and revel in your cash-saving brilliance.
We like this Marc by Marc Jacobs safety pin barrette (pictured) but the $32 price tag isn't in line with our "save for vacation fund" plan. If you're feeling crafty, why not do it yourself?