If I understand how you built the wings as they are on a wire like skeleton, then you should be able to tie on some black elastic bands to the wire and wear it like a backpack.
If you make the loops small, it should be pretty tight when you put it on. If it's black, it should disguise itself rather nicely with the rest of your costume.
I hope this helped.
When in doubt, just take the next small step.
With that next step take a deep breath. It calms the mind.
When the mind is calm you realize the best is still yet to come.