Anything for medium sized parrots, just try an assortment of different things as some love wood to chew, some go for acrylic type but include things that can be chewed, destroyed or dismantled, foraging toys are good too as you can hide treats inside for them to figure out how to get to them. Above all things do include a big heavy duty stainless steel bell, you can find them on the internet, most greys love them and they like to play fight with them, my grey loves her bell and it is the one thing I do not rotate out.
Be sure to take a good look thru the toys and playstands room for lots of ideas of toys especially ones you can make yourself from common items found in the house.