You would need to have a custom hitch extension, and then have a mount attached to that to hold the scooter carrier.

By selecting a product such as Tilt a Rack, or other hitch that is not going to lift by electric motor, it can be mounted to a hitch extension, about 2" above it.

You will have to be very careful not to exceed the hitch capacity. You will also require a hitch extension as long as the lift is wide.

So a 36" hitch extension would be required on a 28" wide lift. Then the scooter rack attached to the hitch extension. The hitch extender will require the hitch weight rating be reduced by a certain percentage, according to the manufactures recommendations.

Your deadweight capacity of 600 pounds will be reduced to about 400 pounds, and the scooter and rack might be 300 pounds, not leaving much capacity to carry a high hitch load. Yet a small aluminum boat, or car that is towed 4 wheels down are possible loads that can be towed behind a hitch extension.

With a electric chair lift, nothing can be towed, as the hitch will need to go under where the electric lift travels. Only rack type carriers will work with a hitch extension.

You might want to post this question on a RV specific site, such as RV.Net They have a section for traveling with disabilities.

Good Luck!