Need intake duct for 89 740 GL

I need a new air intake duct (going from the air mass sensor to the
air intake) for my 89 740 GL. The end at the intake is about 3.5
inches ID, while at the AMM end it is abt 3 inches ID. No doubt it is
actually metric. All the generic air ducts at Autozone have same ID
on each end. To buy the actual OEM replacement from an internet vendor
would cost over $50...for a plastic corrugated duct! I would like to
install a metal one, it would hold up better and NEVER collapse. Could
I make some sort of ring /adapter to go from 3 in to 3 1/2 in at the
air mass meter end?

 

The duct is plastic to allow for engine movement. The replacement should
last another 15 years or so - call it $4 per year? BTW, the duct from the
AMM to the turbo inlet in the turbo version was $150 when I bought one
nearly the years ago.

Mike