I see two possibilities here, either:
a) there does exist a drop-in replacement chip, in which case someone will no doubt help you find it for free. That's what forums are for, after all. Or:
b) there is no such replacement, in which case some reverse-engineering and further design work will be required. The finished article might be manufacturable cheaply in large quantities, but your $150 won't even begin to cover the cost of hiring a professional engineer do the necessary R&D. You're off by at least one order of magnitude, quite possibly two.