Does this tool exist? Perforated disc for making stock
Have you considered repurposing a steamer insert? I don't know how the weight would suit you, but if you're handy, you could probably chop the feet off and add a weight to the top stem thing. Although the feet shouldn't cause too much of an issue. The main problem I foresee using a steamer insert in this way would be cleaning it. But as long as you don't let it sit around, that wouldn't be too much trouble.