70 mm 2.8 macro lens cap
First, thanks to all that replied, been gone over the week end. I found that a 77mm inside mount cap works perfectly. It snaps right inside the hood just as the original cap snaps into the lens, holds perfectly too. Thanks to poster #2 for pointing that out. I tested it out by trying the cap that comes on the sigma 17-50 f2.8 so I order one from Amazon, about $5. Thanks again. Doesn't the end of the lens hood seem a strange place for a filter, flair?