I think that the requirements for dual altimetes and radios only apply in controlled airspace (eg the airways). The requirements outside of CAS are less onerous, but I can't remember what they are. I'm not quite sure how two radios would help you navigate out of sight of the surface - are you sure that the requreiment is for two radio nav-aids?
As always the answer will be in the ANO or the AIP
Brooklands