This partly depends upon your location, as there are typically some restrictions on importation of plant material.

http://www.rarepalmseeds.com/index2.shtml carries many palm seeds, often those that are difficult to get hold of, and I like their service.

Otherwise, there are often some sellers on ebay who sell individual packets, if you can’t find what you’re looking for from a larger stockist.

Check importation rules for your area, as well as the advice of the supplier, on their certification etc.

Hope this helps. Good luck! Rob