Unity told me once, that he was able to find lump at, and may sound weird at first, roofing supply houses. Apparently they stock lump to fire stoves to heat copper soldering irons that the roofing guys use on copper gutters and other copper metal roofing. I had already found a source of lump so I never followed up on it.
I am sure John will chime in when he reads this.
Gustatus Similis Pullus
Large Big Green Egg
Charbroil Gas Grill