Here are my STL files for a wearable ARC Reactor I made, you can use it for cosplay or just to have it because its cool (that's why I made it).

I printed it out to make sure the pieces fit together and fully made one with lights and all, I designed the ring to fit a 90mm in diameter LED and the center one to fit a circular array light, Ill put the link of the ones I used as well. I opted for the harness so you can wear it under the shirt because that's what Tony Stark does in the movies since he doesn't really have a choice I guess. I made my harness with, the buckle STL files but I'm sure you could buy one as well, just ensure that the bands are 1 inch wide.

I soldered the lights to wires and those wires to a switch that connects to a 9V battery (Showed this in one of the pictures)

(I live in Canada so these links may not ship to the US)

https://www.amazon.ca/dp/B078SQ3F68?ref=ppx_yo2ov_dt_b_fed_asin_title

https://www.amazon.com/gp/product/B00ODSBCCA/ref=as_li_qf_asin_il_tl?ie=UTF8&tag=interealinvee-20&creative=9325&linkCode=as2&creativeASIN=B00ODSBCCA&linkId=4700184f7c40d7543c1edd17be76fec8