Questor, there are still comercial suppliers in those quantities. I kept running into them when I was running internet searches for someone to sell me a couple of hundred pounds. They don't sell in my kinda quantities so they were just a nuisance to me. At 5000 pounds, they would be glad to sell to you.
Just run a Google search on linotype suppliers in your state and maybe a couple of adjoining states and be prepared to have to go pick it up.