Otto, I have tried several things with Holland. I've got several different wand toys, with feathers, fleece, bells... she will be interested in them for a few minutes and then be done with them. She loves her little furry mice so I tied one of them to a string and tried to get her to chase it, no dice. She was into the laser light that I got her for a while but hasn't shown interest in that at all for a few months.
Honestly, I think getting her teeth pulled/stomatitis fixed will go a long way toward this issue. Last night I was actually able to engage her in play for about 10 minutes, which is a long time for her, in my experience. She loves to run around my condo, and when she's in "that" kind of mood, she will take off like a shot when I approach her, but I'm not 100% sure if my chasing her is fun or scary for her...

When she's in this mood she will chase toys that I throw for her, and sometimes play with them, sometimes not. I just can't keep her engaged in any activity for any length of time.
It's not like she's overweight (her doctor actually wants her to GAIN about a pound) but she just doesn't play very much. If you have any advice, I'd love to hear it!!