Math Manipulatives for Kids
If you are looking for virtual manipulatives there are various that you could use online in conjunction with Zoom. The sites include manipulatives ranging from Base-10 blocks to number lines.
If you are looking online do your best to avoid any simulations or manipulatives that require a download. Those are typically a signal that they are very old programs and have a high chance of not working or causing confusion to your students. Find ones that work in the browser with no download. If you see anything that says Web App or HTML5 that is perfect. Runaway from anything that says Java, applet, or Flash.
If for any reason there is a simulation that is behind a paywall and you want your students to interact with it, you could call on a student in a Zoom call and pass them control of your computer.