Purchased one of the basic Simoniz ones from Can. Tire a number of years ago for my 1969 Cutlass that sat in a carport. Kept the major elements off but still let dust through and wouldn't stay on with just the elastic ends and grommets ripped with any amount of wind.
Have a Wolf one now but have only used inside garage for dust control and potential rubbing/scratching from other activities in the garage. Can't speak for it's durability outside but it is MUCH heavier material with a thicker/softer inner lining that would appear to protect against light mechanical damage too. Basically I think you get what you pay for with covers, don't recall in detail but the Simoniz one was about $100 or so while the Wolf was significantly more at around $250 but I figured cheap insurance for +$25,000 car....just my 2 cents.

I have a wolf for my 66 Parisienne. the fit is pretty good and it covers the entire car. Certainly keeps the car clean. Have not had any issues with it. Got it from Lordco in Langley and was about $175.00.

Luppy

Coverking covers are custom made also. They are available on costco.ca.

check NationalPartsDepot.  thier Mosom covers are super nice, thick, soft and reasonably priced for chevelles anyway.  Just got a wagon one for 92 USD.   awesome fit and thickness