My rabbits love those cat beds. I didn't think they would like beds, but that style works well. I do find that they tend to use it more if it is in an area they hang around a lot.
There is a local cat rescue here that makes the beds to sell to raise money, they are $20 and very nice quality. I don't know if other rescues in other places make them or something similar, but it can be worth checking out and the money does go to a good cause (even if it isn't bunnies).
There are patterns to make them, but unless you are good at sewing, it might not be a good option.
You might find some used beds. They would need a good cleaning, but can still be used if they are in good condition. I usually will wash at least twice and run over it with a lint roller before giving to a bunny.