You hardly ever find a company that's eager to publish a children's book in an endangered language. That's where on-demand self-publishing comes in: instead of submitting a manuscript to a publisher and waiting for it to be reviewed, you just send files to an online printer. The printer then provides a link, and you advertise the link to people who want to order the book.
I've been in Elton, Louisiana for the last two weeks. In that short time, my Coushatta friends and I have made not one, but THREE books for kids in the Koasati language that way:
First Words in Koasati, by Barbara Langley. Barbara made a baby's quilt with images of a star, a house, a ball, etc. We turned this into a book by photographing each block on the quilt.
A-faa-hil-kas Gracie, by Nina Poncho Fuselier. Nina made this book with her daughter in a language workshop. She photographed a stuffed animal in various locations and then added Koasati and English to make a story.
Ko-was-saa-ti Nas-ma-thaa-li A-saa-la / Coushatta Animal Baskets. The Coushatta make baskets out of pine needles, sometimes in the shape of animals. We photographed twenty of those, added the Koasati and English beneath, and turned it into a book.
All three of these books are "photo books", with better printing for color images. The first two are "mini books" (about 3.5" x 5.5"). The third is 7" x 9".
Formatting these books was pretty easy using Lulu.com. You choose the type of paper you want, binding options, the size of the book, etc. Then you upload the content (text, photos) and choose a format. When you order a book through them, it takes a few days for them to produce it, and then a few days more to get to your mailbox.
The REALLY great thing about on-demand publishing, though, is that you can correct typos as you discover them. That means you can get a draft version out to a language committee, incorporate their feedback, send another draft out to community members, and revise it again when you've heard back from them.
Because of the high cost of postage, it would be hard to make a profit making books this way. But on-demand self-publishing seems like a great way to create small quantities of nice looking books. And it's really pretty easy.