Then I start trying to source them and I find out how rare they are and realize I might never actually be able to find one
A LFS near me might actually have one. I'm going to go check at some point, but the pics I've seen of it it doesn't look ink-black like the one above. I'd spend a couple hundred dollars in a heartbeat for one that looks like that.
Keep in mind, there are hybrids that for whatever reason end up being sold with this name, a discounted fish being sold as granulosa may be suspect.
Take pictures with you or ask the seller for pictures and you could doublecheck an ID in the what is my catfish forum here at PC.