I recently picked up at auction a lot that has several sets of those large folding triangle reflectors that are usually seen behind disabled trucks on the road.
Very heavy duty and well made. These two have a solid bar on the bottom for ballast.
ex:
http://www.uline.com/Product/Detail/H-2589/Traffic-Safety/Highway-Warning-Triangle-Kit?pricode=WY840&gadtype=pla&id=H-2589&gclid=Cj0KEQjw9JuuBRC2xPG59dbzkpIBEiQAzv4-G7CTbAVydu8MHLxk-cwUcTFSIyQn_8hMDGSmbu5gargaArp98P8HAQ&gclsrc=aw.ds
I have way more than I need and have a pair left over to anyone that wants them.
The only criteria is that you be a donating member of this board.
You can pick them up for free from my Dublin Ohio home or I could ship them in a flat rate usps box at your expense.
PM me if you are interested.