Idea 1: things on body, like hem of a skirt.

I would use wire or a chicken coop as a skeleton and then glue paper or fabric over it. The lights would stay in place with the skeleton.
Idea2: some kind of claws.

I could probably buy ready made gloves, or make one out of gauze. Then make long nails out of cardstock paper, or wire and paper, and glue them together. The LEDs could be hidden in the nails.
Idea3: things to hold in hands, like a scepter.

I could make a scepter out of wood or paper and wire and hide the light in it.
Hey Carol! I like the specificity of these LED components. I’m curious what themes/costumes they could fit into and what sort of ideas you’re imagining. In terms of “Wow” factor, I think the skirt would likely stand out the most (though also require the most LEDs). For the scepter, wondering if there might be an interactive element to it? Excited to see where this goes!