I'm not surprised it's hard to get them. Unless you know where to go a curry is hard to get here too. I generally call them and order direct. Last time I did they were 1.5 months out on their orders. (It's not usually that way but they had an issue getting their stainless in stock.)
The main difference between the steel on the curry vs the nela is the stiffness and spring of the steel. The nela is a lot stiffer than my curry. Some of that is because it's thinner but I have a 14x4.5 Curry which is the same as the nela and it's still more flexible. It'd not a ton but noticeable.
Curry trowels are made to order so you can customize the size to be exactly what you want. Standard width is generally 5" unless you ask for something else specifically. (they also make notch trowels, darbys, slickers, etc.)
They do need to be broken in the be their best. I usually diamond stone my edges and set the trowel first thing and it's usually ready to skim right away and just gets better with time. (there is a coating on the steel that's annoying but it comes off pretty quickly.) Let me know if you have trouble and what you might be looking for specifically. Maybe a trowel swap will be I order. I can't find a plaziflex or speed skim over here.