For Dwarf-lore the best sourcebook to start is the Dwarfs: Stone and Steel (WFRP1). On page 36 the book has some (maybe 1/3rd of page) info about the hold.
I dont think there is any problem to change the Karak Azkaraz to Karak Izor. Yes - They are very different types of holds (izor old and large, azkaraz small and younger), but why wouldn't it work…
Here's part from the description:
"Karak Izor ("Copper Mountain") is the first and largest Dwarfhold to be established outside the World's Edge Mountains. Its age and prestige are such that Dwarf settlements across the Vaults, and as far afield as the eastern Irrana and northern Apuccini Mountains, look to Karak Izor for protection and guidance. The hold is ruled by King Kazran Grimbrow and Queen Astrid the Wise of the Izorgrung clan."
- Very rich hold (5 from 1-5). Trade, gems, ore, weapons.
- Estimated population: 20 000
- Garrison: 4000a (this would be soldiers, tunnel fighter, slayers probably - Elite), 800b (these would be watch, militia…etc.