The quipu is a way of storing information in form of knots of strings, as used by pre-conquest Inkas. Although probably not writing, it can be adapted into one - or perhaps reinvented from scratch.
Your entrepreneur devises a clever scheme where individual letters are represented by knots, syllables by "ligature knots", one short string is a word, short strings hanging out of a longer one form a sentence. It is in fact just a simple code of a "normal" orthography, but sufficiently weird to escape the wraith of the "authorities". Quite time consuming to knot manually, but very fast when using a modified Jacquard loom and pre-programmed punched cards. The timing is about right. And for some reason it tooks off like crazy, filling the natural gap left by the absence of printed material.
(it doesdoesn't quite produce the "vector graphics", but hey, it does encode the information...)