Let two radio-buttons behave as one checkbox

Is it possible, without big modification, to have two radio-buttons, which will be displayed as one checkbox?

Actually we're facing the problem, that we're submitting form data which will automatically processed by our system and this isn't possible if we're using checkboxes. Until now we were using two radio buttons (Enable X: Yes | No) but our current customer wants one checkbox instead.

We know, that it would be much more easy if we'd extend our backend, but unfortunaly this is not possible.

Thanks in advance.