What cat toy?

Next week is Mickey & Daisy's first birthday. (link to photos below). So, I'd
like to get them something and I was wondering if anyone has any ideas. I live
in a small studio apartment, and they already have several small rubber bouncy
things which they like. The have a scratchy thing on a doorknob which has a
ringy thing on a string which they play with. They have a large cat tree which
they live in. I was thinking of either getting them a spongy little ball with
a feathery thing attached, which looks like fun. I also have a mouse on the
end of a string attached to a pole which I take out occassionally and torture
them with.I was also thinking of one of those round things with a scratching
post in the middle, which lies flat on the ground and has a track in which they
can push a ball endlessly around and around. It looks like it might be fun,
but I'm afraid the ball would make too much noise and keep me up at night. I
don't really have much room for another standing scratching thing with stuff
hanging off of it.

Of course, I could always just get them chocolate cake and milk. Any
suggestions out there. Small, not too noisy, not too expensive.

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