As far as free corks goes. Mondays is trash day in my neighborhood. Recycle containers usually have plenty of wine bottles in them with corks. Nice and clean.
As I`m walking my dog. I just grab the available corks and deposit them in a container in my work area.
I`ve had to stop as my "supply" is more than enough.
With an excess of corks you can experiment in making things. Some things work out while other "ideas" just hit the floor.
Plus I`v crushed/powdered some to fill in areas on some rod handles. Other stuff included in the mix as well.