Not sure what you are talking about. Smallest ones we ever dropped were 500 pounders and the practice ones were concrete, same size, shape and weight as an actual high explosive weapon. Admittedly, the P-3 not being the most important bomb dropper in the inventory, so I don't know if the pointy nose guys have something like that, but I'm not sure why anyone would be flying around with 100 pound anything. Maybe the T-2s or something. Heck, our some of our sonobuoys weight half that much. some guys use the sonobuoy storage tubes (about 4 feet long and 6 inches in diameter) to fill with sand to weight down the back of a pick up truck in the winter. But, in these post 9/11 days not sure how much surplus/waste military stuff makes it out of the bases.
I have one of the bombs you are looking for, but no, it's not for sale!
It's about three feet long and used to be powder blue in color. The stencil on the side mentioned 100 lbs sand or water fill. I think these practice bombs haven't been used by the military for decades. The ones the military uses nowdays are very small- like mortar shells. I've been in several army/navy and surplus stores that have had a few of the blue practice bombs. You might check there. There are also several army/navy stores online that carry a lot of practice and deactivated ordinance.