Moto-Lita steering wheel adaptors

Hi all
Long time ago I bought one of the 'OEM' GT40 Moto-Lita steering wheels. (I know, I know, it's not original because of the name etched into it....) Now it's time to try and fit it.
Oh joy! Unique PCD - 78mm.
The boss on my steering column is 70mm PCD and I have a horn push badge kit which appears to be 75mm PCD
I don't really fancy drilling my expensive steering wheel so where can I find a 75mm to 78mm adaptor for the badge to steering wheel and a 78mm to 70mm adaptor for the steering wheel to hub?
I've scoured the interweb and ebay but failed to find anything simple. In fact I've failed to find anything with 78mm pcd.
Presumably most who has ever bought one of these steering wheels must have gone through the same pain? I found this thread but no confirmation of final solution -
Any help gratefully received.