It's not impossible - many, many wizards have done it before you. What areas can you access? Whichever they are, be vigilant and look closely -- scrap iron can be kind of hard to see, because it's the same color as many walls, it hides behind crates and water towers. Don't be afraid to ask wizards that you see for help with finding some - I would definitely help out someone who asks nicely.
If you can go into the counterweights, that would be easiest - you just harvest the bottom floor, exit and go in again.
