The portable garage that I have is made by Shelter Logic. They are the same ones you can buy from Northern and other catalogs.
I bought mine factory direct though and picked it up myself. I live only 1.5 miles from the Shelter Logic factory here in Watertown, CT. No shipping charges for me.
The shipping would be expensive on this as the boxes it comes in are very heavy and large. My Chevy Caprice wagon (visible in my attached pic behind the garage) is what I used to get it. The boxes filled up the whole back of the car even with both rear seats down.
This is the only option I have where I am. Due to deed restrictions and zoning issues no additional garage can be permanently placed on my property. The portable garage is taken down in the spring. My Mustang is in the attached garage of the house so my Chevy has to stay outside unfortunately. I hate to do that as it's the other car I work on and doing a light restoration to. I feel bad it has to sit outside.
If I really had the land space, no deed restrictions, and the cash I'd put up a pole barn. I make due with what I have for now though.

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1968 Mustang coupe, Acapulco Blue, 289 2v, C-4, Power Steering.
Hopefully a 1969 convertible or Sportsroof (non Mach or Boss) for next Mustang project
Trying to find my father's 1973 Mustang Grande he bought brand new. 3F04F126773 last known registration and title was in New Jersey, 1982.