<DataTemplate x:Key="ListComboboxTemplate">
        <ComboBox Margin="0,0,0,0" MinWidth="230" Height="22" ItemsSource="{Binding Path=DataContext.ListBoxContent, RelativeSource={RelativeSource AncestorType={x:Type Window}}}"
                  ... >

public class ListItem
{
    public IEnumerable<string> ComboBoxItems { get; set; }
}

public class ViewModel
{
    public ObservableCollection<ListItem> ListItems { get; }
        = new ObservableCollection<ListItem>();
}

<ItemsControl ItemsSource="{Binding ListItems}">
    <ItemsControl.ItemTemplate>
        <DataTemplate>
            <ComboBox ItemsSource="{Binding ComboBoxItems}"/>
        </DataTemplate>
    </ItemsControl.ItemTemplate>
</ItemsControl>

public MainWindow()
{
    InitializeComponent();

    var vm = new ViewModel();
    vm.ListItems.Add(new ListItem { ComboBoxItems = new string[] { "1.1", "1.2" } });
    vm.ListItems.Add(new ListItem { ComboBoxItems = new string[] { "2.1", "2.2" } });

    DataContext = vm;
}