None of the above. First, wait until you actually have a Rifle in hand. Some folks have more difficulties getting brass than others. Some, have trouble getting Toilette Paper. Since no 2 Uberti's are alike, you may not have a problem.
I'm not a fan of "Making up Brass" unless said brass is made from unobtainium or your creating a wildcat. 45-60 is available. It may come
and go from your stockists, but it can be had. While your saving up your pennies for a Knew-2-U 45-60, check frequently for brass. When you see it, pick up a box or two. May even find a supplier or two from here, willing to ship to the other side of the world. Just be careful when you open the box, the cases may spill out onto the ceiling.
Coffinmaker