They have blacklight-reactive letters and shapes on a carpeted wall, which we may eventually try to do. But in the meantime, I was thrilled to find a way to give him a blackout sensory space that's more affordable. I was actually looking for a way to mimic the feeling of being in one of those small inflatable kids ball pits because Mason used to love his Mickey Mouse Clubhouse ball pit. But it popped very fast so we needed to think of an alternative.
One solution is using a black pop-up portable pod like this one one from Amazon. Blackout tents marketed for people with special needs cost hundreds of dollars, but this one is marketed as a dressing room and cost me $39.99. (It needs a wall nearby for stability, since it's made for staking into the ground...wouldn't work for horseplay inside.) With pillows around the sides, a long cushion from an outdoor lounge chair to sit/lean on, and a body pillow across the doorway, the feeling is very similar to the inflatable ball pits. Soft is important so Mason feels safe. I think he approves :)
And the black walls make for an extra layer of fun with toys that light up!