objects for pulling self up!

My son is starting to pull himself up but has nothing sturdy to use! Couch is too high, chairs too high, everything! And if not that, then unstable. Right now he's always using this short cardboard box flipped upside down while I hold it. I was wondering if anyone has any suggestions or ideas for safe pulling up! He uses me a lot while I sit with him, but I work full time and grandma doesn't have the energy or time to get down on the floor with him.