Some companies still offer Custom Orders but be prepared to pay a lot. Not so long ago i made Custom Order for an ESP and the price quote said 12K(!!!!!!!) Of course i didnt order
So beyond the spin of this being a limited edition sig model, dealers can order special runs (custom colours, some config changes, etc.) assuming they place a large enough order. There are plenty out there.
If you could guarantee selling 50ish instruments, you could probably get your own sig model too