For your rear brake conversion, the handle is easy just buy a dirt bike clutch lever and perch, many options and colors.
The cable shouldn’t be too hard either, TerryCable used to make custom cables by dimensions, there are probably other companies that make custom cables too.
Any bike that has ape hangers will have custom cables and hoses.
Give Terry Cable a call, they can probably make you a front cable.
Remember the Aero 125 was called a Lead 125 and sold for many years in other countries, I would search the bike shops in England first, to find that front cable.
I bought most of my Aero 125 parts from England and Netherlands, pretty easy once you get the hang of it.
I really like the right foot brake, it is in the correct place and matches all my motorcycles.
The left hand is for a clutch in my opinion.