Water Bath Weight for Two Hose Connector Bottle Top

I use special bottle lids to replace air with nitrogen in culture media storage bottles. When their liquid volume is low they have a tendency to float-up in the water bath and fall over, requiring the remaining media to be thrown out.. 

They sell plasti-coated metal bottle weights to solve this issue, but the normal ring-shaped weights don't fit these special lids.

I designed this custom bottle weight to sandcast my own bottle-weights in bronze (90% copper 10% tin). Weighs around 115g, which is more than enough for the 250mL bottles I use.

Printing with 100% infill from a heavy filament like Colorfabb copperfill is an option that doesn't require a metalcasting setup. 

Note: Model for the shown barbed fitting caps is available here.