Unless you go with 3D printing, which has its own issues, a custom enclosure is the sort of thing that will only be possible if you can sell large volume of your product. This is one of the benefits of using kickstarter, if the campaign is successful then you already have the sales volume and the money, if it's not successful then the demand for the product may not exist at the level that will support custom enclosure manufacturing.
Of course it's not necessary to use a custom enclosure. You could just find a source for nice enclosures of a suitable size. You should be able to get them cheaper if you buy large quantities at one time.
Luckily custom PCB manufacturing is now quite accessible to anyone even at small quantities.
There may be some significant bureaucratic barriers to overcome before you can bring something like this to market. It seems like people try to get around this by selling kits. I don't know all the legal details on this sort of thing and I'm sure it changes from one country to another. https://www.tindie.com/ is probably the marketplace of choice for selling that sort of thing. Unfortunately a lot of potential customers are not going to be willing to do the assembly but you may find there are enough to still make it a viable product.