On Facebook yesterday, I saw a post about a rabbit and it was cuddled up in a cat cave. As well as I remember, it was more like the ones found in pet stores as opposed to the felted wool ones on Etsy, but this rabbit evidently had no hesitation about snuggling into one, so maybe Acorn would like one too. The ones in pet stores are a good bit cheaper than the ones on Etsy. The pet store ones are usually plush or quilted material. I see one at Petco that is on sale for $20.99. It also comes in gray.
http://www.petco.com/shop/en/petcostore/product/petco-restful-snuggler-pyramid-cat-bed-in-brown#
That’s not as whimsical or shaped the same as the ones on Etsy, but it or something like it would be cute and different. Although, you certainly don’t want Acorn to chew on them. Most of the ones in stores probably have some kind of fill material in them, so that could make them more dangerous if ingested. If you have any pet supply stores near you, you might want to take a look and see if there are some ones you like.