Reverse mounting adapter

Hi all

Does anybody know of a coupling adapter to reverse mount an El-Nikkor (N series) lens to a 42mm bellows? In other words a 40.5mm male to a 42mm male threads. I can do it with more than one adapter, but would rather have a single piece if I could.
I have searched fleabane and several camera suppliers but to no avail.
Has anybody any ideas?

The closest i could find was a 40.5-52mm adapter so thats no good, are you/do you know anyone handy on a lathe? might be the only solution?

Thanks Dubstylz,

I think you're right, I could only find similar adapters going from 40.5 to either 52 or 58mm.

I can of course get one of those and also a 42mm to 52/58mm reverse coupler, but I was just trying to avoid using two adapters if I could get a single to do the job.

Anyway, thanks again for the reply.