If the selection is already made you can simply use
selections are honored when features are copied
There is no specific tool for model builder to perform a manual selection
Ok- I am still lost on how to convert the rectangle to a feature and export it.
If I had drawn the rectangle around the area outside of the model- in the model I only convert?
Perhaps you had better elaborate on the full extent of your model and what other tools you intend to use, since certain tools allow you to draw features on the map to use them as input for processing.
If your intent is to simply produce a polygon/rectangle, you don't need a model to do that, simply create a featureclass and draw the geometry, then save your edits.
You can do this in ArcTools by creating a custom tool and then add your custom tool to ModelBuilder. It is not clear if you want to avoid any Python programming, but that is the simplest way to do exactly as you asked.
You create an empty template layer (for geometry type, fields and symbology). Then you create a new tool and set the dialog to input a featuredataset (it needs the template). When the tool opens it asks you to draw some graphics similiar to the graphic Draw tool. You can also set attributes if needed, there can be more than one feature. It is very flexible.
When the tool executes it passes the featuredataset as a parameter. This can be turned into a featureclass and exported as an output for use in the ModelBuilder chain.
Interacting with the map in a script was always much easier to do in Workstation/AML and later ArcView/Avenue.
If you are still interested in this approach I could post an example script.
Here is the help where I needed the user to sketch a proposed marine reserve:
Create MPA from Sketch or Features
Zoom to the area
Use the interactive sketch tool to draw polygons on the map
You can use the graphic tools to draw circles, ellipses, rectangles or freehand polygons
You can edit the graphic shapes, adjust vertices and in the graphic properties adjust to an exact coordinate
When you select [OK] the parts will be assembled and saved to a new featureclass with the default name or the one you specified.