I used Atsko permanent water guard, and it worked amazingly. They also sell sport wash which is a detergent free wash that you can wash your waterproof gear in the washing machine with, and it won't detract from the waterproofing ability of the factory DWR treatment.
You can buy it in a 10oz aerosol, or you can buy it in a gallon and have plenty extra. Put it in a spray bottle, and go for it!
Waterproofing | Permanent Water-Guard Gallon
Whatever you use, make sure to use a polymer based treatment, and make sure to wash it with a detergent free wash before treatment since any dirt or oil residue will have negative effects on the new DWR treatment. After its clean and you wet it down with the treatment, you have to then heat activate the polymers. You can put it in the dryer if you plan on replacing the gaskets as well, or you can iron it on low (thats what I did).
Also another thing...if you clean it with a detergent free wash and then heat it - either dryer or iron - you can restore a lot of the factory DWR's performance without needing retreatment. If the top isn't that old I'd try this first. If its older, just go ahead and retreat.
I've also heard a lot of good things about McNett ReviveX