You want the functionality of a checkbox combined with the look and feel of a radio button. My suggestion is to use a checkbox (a boolean attribute) and play with the styling.
You can use an enumeration with 2 empty captions for this.
An alternative solution would be to give the radio buttons a class, and remove the labels of the radio buttons using CSS.
As an alternative, you can also use images with conditional visibility (boolean or enum). When clicking on the image, you could use a nanoflow to toggle the boolean to the other value (not($boolean)). You can also use this approach for a styled container.
There are many ways to approach this; hopefully this helps.