I have some naga viper seeds but no extras at least not yet. I bought mine from Gerald Fowler in the UK. The strain started with him. He says it has been somewhat stable for 2yrs now but does throw out the occasional Trinidad Scorpion every now and again. Here is his web address where you can order just know that with the current exchange rate out $1 is $1.63 in the UK and there is a slim chance your seeds could get snagged in customs but I've ordered twice without issue.
http://www.chileseeds.co.uk/
I'll have some seeds next season that is if they are what I've heard they are.
http://www.chileseeds.co.uk/