You would have to call them and see. I don't know if your vet will require that you bring your rabbit in or not. Yes, I would suggest saying this is for a rabbit.
Revolution seems to be the safest and most effective flea treatment for rabbits. I would use it over Advantage any time. But as with any medication, there is always some small possibility of an animal having an adverse reaction. So though it is generally considered safe, nothing is completely without risk.
If they give you the right flea medication, which is Revolution(selamectin), and it's a tube for a 15lb cat/dog, then it would be the right dose for your rabbit. Rabbits get 3 times the cat/dog dose. For your rabbit at 4-5lb(2kg), the dose would be approx. 32-50mg(25mg/kg dose was used in the rabbit study). A single tube of Revolution blue box for 5.1-15lb cats, is 45mg, and would be about the right dose. Or 3 tubes of the puppy/kitten box, that are 15mg each tube, together would be the needed 45mg. If your rabbit is right at 4lbs or just under that, then one tube of the 30mg purple dog dose could be used instead.
If you have to buy the whole box, and don't want to keep any extra on hand for another time, I would get the kitten box and use 2-3 tubes, depending on your buns weight. If you only have to buy a single tube, I would get the 30mg purple dog tube for under 4lb rabbit, or the cat blue tube for over 4lbs and up to 5.5lb rabbit. If you have to pay for a whole box and want to keep extra on hand, I would get the purple dog or blue cat box. And just make sure it's the regular Revolution and not the Revolution Plus.
Frontline(fipronil) is the one you should NEVER apply on rabbits, as it will kill them. So that is the one flea treatment that you have to be absolutely sure is never given to or around your rabbit.