lol try the pink dandelions, and reg too. They drop everything from stone block to springs, even black pearl which you'll need in mooshu ;) Also i realm jump sometimes in Chealsea Court. Use the teleport central as a start point and go to each then try again. you can actually get quite a lot.
MB is the best place to find it. I have farmed a lot for Scrap Iron and always go to MB late at night. Have you tried switching Realms to "perfect Realms" in which less people are playing?
I would suggest you go to Knight's Court or Chelsea Court and hop between the 3 teleport sites looking, then switch realms and hop the teleports again. It takes about 1 minute to search all 3 and the station location. You will also find stone blocks and some mist wood. You will get familiar with the spots it frequently shows up after farming it awhile. You can also find it running around the Regent's Square loop. As with all it helps to farm when the game is not crowded or busy.
You can sometimes buy it at the bazaar, but it sells fast and is pretty expensive.
You can also craft Scrap Iron using a Transmute spell - it cost 10 stone blocks and 10 ore. I think the Reagent vendor in MB sells the Transmute recipe, not sure.