One of my neighbors brought her bike to me today. I figured it was for a minor fix, since I am the "Bike Guy" in the 'hood.

She had a Rhode Gear u-lock with a bad key - one of the points on the barrel key had broken off. I know that Rhode Gear is defunct, but there has to be an easy way to duplicate the key (it has a number). My local hardware store shot me down, and I would rather not grind it off with a cutting wheel.

Any thoughts?

I'm not familiar with Rode Gear specifically, but have you tried the bic pen trick?
Alternately, it might be possible to insert the key and use a dental pick or other probe to manipulate the tumbler at the missing post.

Any chance there are two keys?

You could try a locksmith. Having the old key as a pattern would help.
A welder, jeweler or watch-maker might be able to build up the old nub and grind it back down.

None of those options would be cheap, and you'd probably spend more than buying a new, more secure lock.

You could also probably make a key from scratch using some tubing and a file, although there appears to be a pin inside and out, is that required, or just to orient the key?

Maybe the locksmith would have blanks.

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...the last one I cut off with an angle grinder took about three minutes. Maybe you're overthinking this ?

I got it - it was a brain fart. Remove brake levers and shifters, remove bars, drop the stem, and voila.