Advantage can also be found on-line or thru some pet stores (I have seen it at Petco I believe). Usually I am not a big advocate of buying on-line flea meds- but if you are purchasing from a reliable source such as maybe Doctors Foster and Smith the risk of getting a counterfit product should be minimal. Advantage should be available for purchase without a prescription- just make sure it is straight Advantage- treats fleas- nothing else like intestinal worms, heartworm, etc. Make sure you are getting the appropriate cat size for your bunny based on weight. How much does Pacey weigh?
Revolution is also commonly used in bunnies- but it has a heartworm prevention in it- so it is a prescription and you would need a prescription from your vet to buy it on-line or at another vet.
I have not ever ordered fleas meds or other meds on-line- so I am not sure the best place to look. I would avoid e-Bay as there is no control over the product and counterfit products would be more dangerous to a rabbit than a cat. Maybe others have some suggestions?? But I personally think it would be better to treat with a great product that really works, like Advantage (or Revolution) than to use out-dated (in my opinion) powder methods. Since you have fleas in the house- you should take steps to avoid re-infestation due to the flea lifecycle. Do you have any other pets in the home?
How long have you had Pacey and in what areas of the house has he been in? and do those areas have carpet?
If you want to be 100% sure that you are killing all the fleas and killing the fleas that have not hatched yet- topical flea treatment for 3 months in a row for all pets is recommended. But if you did not have Pacey in many areas of the home- it is possible to maybe get away with less- with vacuuming and emptying the vacuum right after (immediately- get it out fo the house as it will have flea eggs it has picked up and those can hatch in the vacuum). Wash any bedding that the pets have been on.
The flea comb method/soapy water works well to control the adult fleas that you find on Pacey- but if you want a topical method that does not require as much labor, or is someone has a flea phobia (like I do)- topical are very convenient.
EDIT- I just read that you have dogs (not sure how I missed that the first time)- if you are treating the dogs with anything topical- if it is not rabbit recommended make sure to keep the dogs away from the bunny until it is completely dry. Cats and bunnies can get ill from coming into contact with the dogs flea/tick meds from playing with them. (It should not take more than 2 days max to be safe for contact). I use Frontline on my dogs because I get free product from the company rep- so I just make sure I don’t let the bunnies play with the dogs for 2 days. Actually one of the rabbits likes to try to boss the dogs around. Just be sure to check the active ingredient to know if you have to limit contact.