Hi...I see what you mean, there seems to be a lack of courses and info in the UK relating to native American culture and tribes/language. I did notice that the University of Essex has several native American Indian specialists so maybe you could contact them (you might need to try more than one person or write to the general secretary, as academics are so likely to be away at seminars, on sabbatical etc (lucky!). I'll try to give the link but I'm not sure if I've copied it correctly...if not, then you'll be able to work it out, I'm sure. www.essex.ac.uk/~phulma/nativeamericanstudies
I hope you manage to sort it out and good luck with the course
The only other thing I can think of is to get in touch with the central Tribal Council in the USA but it might take some time to get through to the right people, especially as you say it is a dead language.