At first the thought of actually spending decent money on materials to fill my Osiris stands was out of the question, until on I whim I gave the folks at www.audiopoints.com a call and ended up filling my stands with their "Micro-Bearing Conductive Steel Fill Material". Was a major improvement over sand filled.
Would suggest you give them a call. Some of the most helpful people I've talked to, and you can hear their interest and knowledge in the conversation instead of a typical sales pitch, or worse, a sales pitch without knowledge behind it, or someone that doesn't know more than a product brochure.
They'll end up asking exactly which models you have, what speakers are on top, sizes, weights, everything and give you an estimate on exactly what you need and how much.
Even if you are hesitant or straight up not going to purchase it -- give them a call. First time I was on the phone with them, I didn't end up making a purchase, but spoke for over an hour and got quite a lesson and opinion.
Check them out. Benefits were immense in my application.
I'm sure others will chime in with many other alternatives as well.