As mentioned above, with that budget you really won't be able to find a decent brand new monitor that has that feature.
To meet those criteria I would look for a second-hand Dell Ultrasharp monitor - as these are good quality and come with stands that swivel to portrait mode. They also tend to use non-TN panels - so the issue with vertical/horizontal viewing angles when running a TN panel monitor on its side are avoided.
As for what specific monitor to look for I would strongly recommend the Dell Ultrasharp 2209WA. This is a 1680x1050 22in E-IPS panel monitor with a VERY good reputation. If possible, get one with the original box and some warranty remaining.