Here are some things my kitties love to play with: catnip puffs (very inexpensive at Petsmart….just like colored cotton balls soaked in catnip), plastic drinking straws (scooting them around a tile floor or chasing as I drag them across the floor or up the scratching post), lightweight plastic things like milk jug rings. They also love cardboard boxes of various shapes and sizes and paper bags. Of course, a second kitten is the best plaything, but I know that isn’t an option for everyone. (And it doesn’t do away with the need to keep them entertained. I have three and still spend a lot of time meeting their play needs.)
In my experience, on of the most important (and funnest) parts of being a kitten mom is interactive play…having certain toys that they have to have you involved to play with. Examples are wand toys (“daBird” is a good one) where they chase something on a string, dragging string for them to chase (never leave it out with kitty unattended…very dangerous if swallowed), or laser pointer (a big hit at my house.) The kitties are so cute practicing their “hunting” skills with these types of toys. Mine look forward to this time every day and I think it makes for better behaved kittens.
Your kitten might also be entertained by having a window perch or special spot where they can look outside. Mine really enjoy that as well.
Good luck!