Where can I find sayonara sales in my city?

Hello Antonio, for the sayonara sale or giveaway,You can try the websites below:
https://classifieds.gaijinpot.com/index/index/search/tag%3Asayonara
http://www.sayonarasale.com/

I would also recommend searching for sayonasa sale groups on facegroup.
you can type something like:
"Sayonara Sale Osaka" or Sayonara sale Tokyo and you may find many things.
Like this group for example: https://www.facebook.com/groups/osakasayonarasales/

Craigslist is another great place to look for cheap furniture:
https://tokyo.craigslist.jp/search/gms
https://tokyo.craigslist.jp/search/fua?query=BED

You should also try to search "moving away sale"
I hope this helps!