Some time ago I had the same issue with a shroud. I took a piece of 1/4" thick black nylon plastic material (had it laying around the garage... used it to cover a workbench) cut it into a strip and rivited it to the top of the shroud to fill the gap. Make sure you make a cardboard template first, as it will be kinda cut with rounded lines to conform to the shape of the shroud so it looks good. Slapped a "Caution Fan" sticker on it too. Worked well, dosent look bad as long as you evenly space your rivits on the material you use.