online or off, I have not been able to find one place that lists hatchets as in stock. I think one place had silver ones, but no one has marbleds. if your local petsmart has them, set up a tank for them and get them!
I haven't seen marbled lately either but I still see silver around. I have 6 silver hatchets and love them. They school pretty well and keep the top of the tank nice and busy which is nice in the relatively tall 37g I have them in.
Keep them on your short list of fish to pick when room is available! Fun fish
Congrats! Also, that one inch per gallon rule isn't a rule at all, its a myth. Don't follow it AT ALL, EVER. You should know each fish you have's individual needs and go by that. These forums and other websites on the internet can tell you all you need to know.