Hi Jason,
'Invacare' and 'Merit' buy Scooters from manufacturers, and have them 'Badged' for their companies.
You will probably find thet their scooters are either 'Shoprider', 'Freerider', or some other big companies product.
Most of the mechanical parts for the scooters are made by one of the big companies, and are (generally) interchangeable to a certain degree.
If you are unsure, then wait, and see if you can find a complete, working scooter to use. You might be better off in the long run.
Hope this has helped,
Regards,
Mark.