The find by property code in this documentation is what you are looking for: https://learn.microsoft.com/en-us/bingmaps/spatial-data-services/query-api/query-api-sample-code-csharp
Alternatively you can use the https://github.com/Microsoft/BingMapsSDSToolkit There is a nuget package for this here: https://www.nuget.org/packages/BingMapsSDSToolkit Here is a code sample for finding by property: https://github.com/microsoft/BingMapsSDSToolkit/tree/master/Docs#example-find-by-property
As you know, Bing Maps is retiring. Azure Maps is unlikely to create an alternative for the Bing Spatial Data Services as there is lots of other options for data storage and access in Azure that provide a lot more security and capabilities, and would cost significantly less.