Usually I find something at Warmaiden's - make sure you go inside the shop first, then go talk to Adrianne outside (sometimes if you do it the other way, both Adrianne and Ulfberth have the same stuff - and if they're BOTH in the shop, they definitely have the same stuff). Occasionally, whatshisname in Solitude has had something, or failing that, whatshisname in Riften.
I usually go outside first then inside, however to both in the morning and go straight from one to the other, then the lady goes inside they will get the same inventory.
Also check the drunken huntsman, the general store and the skyforge might also have something. you might want to fast travel around look, this way you can also sell lots of stuff and buy other rare items.