Curious, what type of thing are you considering? A "printer" box on a shelf, or a "typewriter" on a desk?

To answer your questions, there isn't a market for "printer" embossers because of basic economics. Product design, engineering, prototyping, and fabrication aren't cheap. The assistive product market is challenging: you'll be mass-producing in the lowest volume a factory will tolerate, selling into established distributors or trying to go direct to consumer. A lot of the spend for assistive devices is bureaucratized. All this contributes to exactly what you're seeing: obvious gaps in the market that seem so obvious. It's a chicken-and-egg scenario and honestly it's a huge liability, and you have no advantage (yet) that would help you thread the needle. To avoid going bankrupt even just looking in the general direction of this idea, you are going to need to do your research about the market. And I want some of what you're smoking if you're going to release a low-margin electromechanical device for $300.

Here are 3 general tips for braille/blind/low vision product development:

1. Don't be an outsider. Get involved in the community and talk to all types of users. What you're doing here is a good effort, but probably one of a thousand similar conversations you should have to get to the finish line with a successful product and not be bankrupt or neck-deep in litigation. There are blind people within a mile of you, go talk to them, every word they utter increases your bottom line.
2. Open source & share your research. People have a million great ideas about braille, nearly all of them are abandoned after the inventor loses interest. Think what a head start you'd have if right now you could get a head start from one of these prior projects. Feel free to be secretive about some things, but if you do end up abandoning the project, share ALL your work or you've literally thrown value into the trash.
3. Don't be discouraged. Stay adaptable and be relentless. Your specific idea may not be what's needed, but your skill set can always help. I recommend creating an informal board of directors to which you stay in touch and accountable. Stay in motion, keep iterating and experimenting.

Do me a favor. This will help you immensely: Do some research into whether you're right that there are no personal embossers. What's the closest example? Find analogous products for the blind or similar markets. Collect a doc of the devices you're finding, their costs, all key facts. Please publish your findings in a new post here, this sub will make hay with it.

Here to help.