I'm not 100% about whether this will work, but give it a try. Once you have a reference to the container, use the 'Value' property. This will give you a variant. From here you can use Variant to Data, connect a MediaPlayer constant reference to the type input and you should get the correct reference out.
Also, you could simply get a reference to the VI with the ActiveX control and use the method 'Control Value: Get[Variant]' to get the value of the control instead of getting a list of all the controls and searching for the one you want.