Yes, bunny cremation is possible. I've had to take two bunnies in the last two weeks. It cost £70 for a medium sized bunny. £60 for small breed and £80 for large breed. This is with Dignity our local pet crem. The price includes the rabbit being returned to the owner in a bamboo scatter pouch.
You can also have bunnies cremated in mass cremations without them being returned to you and I imagine this would cost less (not with Dignity but with company called Summerleaze who are in Wales - your vet can organise this when necessary I expect).