*Ingot - sorry.

So I'm power-levelling my smithing by buying iron ingots from the guy in Whiterun and then making iron daggers but when he runs out of iron bars it takes ages for them to come back.

Does anyone know of any other places where I can buy a decent amount of iron ingots?

1 city? near river?

Most smiths sell them. Also, there are two sellers of iron ingots in Whiterun iirc. The chick who works the forge and the clerk inside the shop adjacent to it.

Hitch a ride to Riften and then break into the blacksmiths at night. He has a bunch down in his basemant.

There is a much cheaper way of doing it- go to Halted Steam Camp (its NW of Whiterun, you get sent there for a bounty) and mine all the iron- a full run should net you around 40 or so ore.
Then just get some leather and make a tonne of daggers.

There's 3. The guy at skyforge sells it too.

Many mines have iron ore, and not necessarily the ones that are specifically "iron mines". For example I found iron veins in ebony mine etc.