ReactiveUI - ReactiveCommand to get more data for objects in ReactiveList - reactiveui

Question

Currently I am learning ReactiveUI and I am not sure how to approach this problem. What I want to achieve is once a reactive list has been loaded (in this case I am using a command to load it from a local store) I want to be able to trigger that each of the items in the reactive list then go off and fetch data from an api endpoint and update the view model.
What I currently have to load and create the view models using this logic:
LoadSavedLocations = ReactiveCommand.CreateAsyncTask(async o => {
var savedLocations = await _savedLocationService.GetUserSavedLocations();
return savedLocations;
});
LoadSavedLocations.Subscribe(savedLocations =>
{
foreach (var savedZone in savedLocations)
{
Zones.Add(new ZoneDetailViewModel() {
ZoneId = savedZone.ZoneId,
SavedName = savedZone.SavedName,
});
}
});
I want to then be able to have a command that I can kick off (one first load of the screen and then when the user prompts for an update - pull for reload).
There are two ways I think I can do this but struggling with the approach and the code to achieve this.
Option 1
A command which loops through the items in the ReactiveList fetches data from the Api and then updates that viewmodel something along the lines of
UpdateZones = ReactiveCommand.CreateAsyncTask(async o =>
{
foreach (var zone in Zones)
{
// Fetch
// Await
// Update view model
}
return null;
});
With this I am confused around what the return type of the command would be just a new object()? Is there a better way than just looping like this?
Option 2
On the view model ZoneDetailViewModel have a command called FetchExtraData which will then return the data from the API and I can subscribe to that command in the view model and populate the extra properties. With this approach how does the parent viewmodel trigger all the items in the ReactiveList to fire their commands.
For both approaches I don't know how to get each of the items in the ReactiveList to do logic which involves going to an Api and update.