I know it can be difficult for you where you live John.
But like everything else, I would like to make everything myself, but most times, with something like this, I would always go the route of buying part machined backplates, as they already have the correct registers machined into them. In fact, for me to make one, although easy enough to do, it would be twice as expensive to purchase the material plus the time spent making than buying a commercial one.
In fact, I will be purchasing a couple of spare backplates soon, when I next prepare an order. It will be handy having them in stock, just in case I come up with a new idea for some new tooling I want to make. I already do that with blank 2 & 3 MT's and R8 arbors.
To me, it isn't worth not having them in stock if you are into making bits for your machines.
John