How many CC's do I need?????

I'm new here, so be patient, I'm looking at buying a scooter to get to
and from my place of business. This $4.00 a gallon gas is killing me.
I live in a rural area about 25 miles from my shop. Most of that
distance is highway traffic at 60 to 70 mph speed limit.
I don't want to get run over or off the road by the car/truck traffic,
but I'm unsure of what size scoot to get.
I'm about 5'9" and 180 lbs (yeah...short, fat, and bald) and will be
riding alone on the scoot. I'm not worried about ever carrying a
passenger or anything. Anyway, I'm totally ignorant of engine size
(cc's) and brand. I see a lot of "made in China" stuff advertised, but
am unsure of their quality. I'm familiar with Yamaha, Honda, Suzuki,
etc. as I rode motorcycles for years and I know that their quality is
always top line.
Any advice ya'll can give would be appreciated.
SpongeBob (Needing a Scooter in TEXAS)