James at
http://www.blaberus.com. He sells females for $2 each, and breeding pair for $3. He does not require you to purchase orders of nymphs. He sets the cap low however, I doubt you'll be able to get more than 25 females, as he needs every one he can get to meet his dubia orders. He sells more retail dubia than anyone...
Roach guys sells adults with orders of nymphs only, and I do not know how many he has to spare. His colony is medium sized, so probobly not many.
http://www.dubiaroaches.com sells adults, but I believe you have to purchase nymphs in addition.
http://www.blapticadubia.com does not sell adults.
I do not sell adults either.
Adults are going to be hard to purchase, and if you find them they are going to be expensive. Every breeder I know is hoarding their dubia stock, as demand is very high at the moment. The few who sell adults, especially females, do so very sparingly. I personally do not see the benefit of selling adults, regardless of the price. The few times I have, its always been a mistake. I once even gave some away for free....just to have them get cooked during shipping.
Never again.
I hope my list helps you find some.