If you click on where it says "disABILTIES" at the top of this page it will take you to the Index. One of the top items is the "disABILTIES FAQ" which will gives lots of useful information. Post #2 gives information about rental of accessible vans.
However, most ECVs are designed to be broken down to put in a car trunk. Check Post #5. Generally the heaviest piece is in the 40-50 pound range on most full-size ECVs. If someone in your group can handle that it will be much less expensive to to rent a car or minivan or SUV than to rent an accessible van.
Or, if you want an easier route, click on the link in my signature.
If you want to be able to drive it right in, then you need a wheelchair ramp or lift van. There is information about companies that rent them in post #2 of the disABILITIES FAQs thread.
If you are planning to bring/rent a collapsible ECV or one you can take apart, you could get it into a large can trunk or can use any van. I'd suggest a Chrysler extended wheelbase van (Chrysler Town and Country or Dodge Grand Caravan). Those have extra space behind the back seat. Some also have Stow 'N Go seats that allow a seat to be folded flat into the floor if it's not needed. That gives more space for objects like the scooter. And, if the seat is in use, there will be a bin on the floor the size of the seat that you can use for storage.
I am not sure the size of your party or scooter, but I rented a Nissan Sentra and just put the scooter in the trunk.
Sat 4 of us and lots of room.
I took off the seat, collaps the handle, if you have two lift it into trunk. when I was alone with my dd I would remove the battery so it was lighter to lift.