There are no vendors with large selections of moss species to grow. Your best bet is to inventory everything you can find on the net. Also keep in mind that you can find mosses in nursery grown pots of regular flowering plants locally in some cases.
You may want to try to collect interested species on your own if they occur near you. Also you should check eBay as some mosses are offered off and on there.
Same with Lycopodium. Very few species can be found on the net for sale. eBay is your best bet with these.
Dawsonia! Far as I know it is not grown in this country even in any university greenhouse but ??? However, I have contacted a New Zealander to see if they can provide spores as spores can be sent international with no problem unless the species is CITES restricted on any plant material of the species. Will post or contact if I get a positive response.

Hi
Do you want temperate or tropical,terrestrial or epiphytic?? You can get specimen size lycopodium squarrosum from Gardinos.. If you can wade through the mess maybe Glass house works?? lol You could ask "world plants" to do a search for you. They found a couple of very rare plants for me. gary

thanks for the help! i'll be checking back periodically, or pm me.

I live in Eureka Springs, Arkansas and this post came up when I was hunting for moss species I could use here to create a moss lawn. Is there any update on your findings that could help me with mine? I’d be so glad for an informed head start. Thank you!