I am going to need a replacement  cover for my 680, any suggestions?

I went through waaaay too many covers on various grills.  I finally bought substantial ones.
 
Do an Internet search for Covers By Mel. It will last so long that your grandchildren will be using it.
 
My only complaint is that the material is so heavy that they are difficult to handle.
 
She can make custom covers if you send her good measurements.

 Not a H D custom cover - Mountain Grilling Gear, sold @ Lowes and other locations, fits my Memphis well. The quality is good, has welded seams and good vents..There are different sizes available.

 If pricing is a consideration this may be the ticket. Being lighter weight material it's easier to R/R than a custom cover.. As pmillen stated the custom covers will last, are heavy and initially less expensive.

Look at the Ravena covers on Amazon. Heavy duty and affordable.   They last about 5 years.

Look at the Ravena covers on Amazon. Heavy duty and affordable.   They last about 5 years.

This is what I use.  I believe I bought the large one. 

Look at the Ravena covers on Amazon. Heavy duty and affordable.   They last about 5 years.

This is what I use.  I believe I bought the large one.

I bought something similar to that if not the same thing in a lighter color years ago.  They seemed heavy and worked well.  I was just to lazy to take them off and put them back on so I quit using them.