$1That isn't exactly what you asked for, but it is a guide to building what you want. With 3D printing, keys can be placed at any height, angle, location you require. The 2 halves can be joined by cable, or wirelessly if each half has a power supply. I can help with the electronics if someone else can do the 3D printing. I'd like to learn to use a split braille keyboard.
Macro pads are an existing mass produced product with wide DIY interest. Two of those could be pressed into service as a split Braille keyboard with the right firmware and drivers. A special USB hub may be necessary to make the seperate HID devices appear to the computer as a single composite device. SDF on the left JKL on the right like a Perkins Brailler.
Another method would be to buy a regular Qwerty split keyboard and remove all the keycaps except S, D, F, J, K, L, Enter, Space, Arrows, and whatever other keys you require.