Honestly, I doubt that a new zealand bred bun is a vienna carrier, and it's most likely he will be just fine with ivermectin. Most rabbits are, but yes there is always the possibility with any med, that a negative reaction can occur. I would probably just go with the ivermectin since working with this vet is turning out to be so stressful. To get it right away, tractor supply or another feed store should have it, or online if you aren't in a hurry. The name brand is ivomec, but that is more expensive. I would get a bottle of the generic if they have it. It's a 1% solution, so has 10mg/ml. So to get the 0.4mg/kg dose, that would be either 0.04ml/kg or 0.018ml/lb. For a 3kg bun that would be 0.12ml, and I would just draw it up into a 1cc tb syringe with a needle, then take the needle off(make sure the syringe has a removable needle) and squirt right into the mouth. If I was concerned about a possible negative reaction, I might try a minuscule test dose of maybe 0.01ml, then wait several hours. If there didn't seem to be any negative effect I would go ahead and give the normal dose. Giving an extra 0.01ml for a 3kg bun shouldn't be harmful as there is normally a wide margin of safety before an OD would occur. Make sure to retreat 2 more times, 14 days apart(refer to dosing directions in previous links posted). Not saying you should do all this, just what I might do. I have used ivermectin to treat mites before without any problems. But I do know of cases where ivermectin toxicity has occurred, so it can happen.
https://www.amazon.com/dp/B004FVUH6C/?tag=skimlinks_replacement-20
If you still want to go with revolution and it's not immediately needed, I would tell my vet I'm going to order it online and that the company would be in contact with them for the prescription info. Just find a reputable one with the best price, and look at their instructions for getting vet approval. It's usually just a matter of you placing the order and them verifying the prescription with the vet. I've ordered from Drs foster and smith, and they usually have decent prices, though there are plenty of other places to order it as well.
https://www.drsfostersmith.com/product/prod_display.cfm?pcatid=9567
Cat and dog revolution only differ in their strength. Cat revolution has 60mg/ml, dog revolution has 120mg/ml. The dog revolution would be the cheapest way to go, and for a 3kg rabbit that needs about 60mg, that would only be 0.5ml that you would need to apply. Dogs and cats get 6mg/kg, so you basically need 3x the amount, which would be the brown box(10-20lb). Or if you have several rabbits you need to treat, you can get a larger tube and just draw up the appropriate amount for each rabbit into a syringe, then apply according to directions to the back of their neck. You just pick the box with a tube that has enough to split up and administer to all rabbits that need treatment. It usually only costs a few dollars more for the larger tubes. The 3pk of brown is $50, and the 3pk of teal that has 4x as much is only $2 more. Use one tube, then save the others in case you ever need it again. Apply according to directions, and if you have buns that live together, you may need to separate so it has time to dry and won't be groomed off by their partner.
https://www.zoetisus.com/contact/pages/product_information/MSDS_PI/PI/Revolution.pdf