Try these guys: http://www.topbulb.com/

You might find something on this page:
http://www.topbulb.com/find/prod_lis...10_A_REF_E_130

They have a wide range of bulbs and an 866 number. You probably won't
find an exact replacement, but as long as it fits that's all that's
needed.

I understand your attraction to fixing an old clock radio rather than
buying new. The old ones are unique.