They are all over Amazon.
Just do a search on suspender pantyhose. Honenna has some cheaper ones, but if you can afford it, Mila Marutti makes some really divine stuff. They gave a white, red and beige.
Red is sexy. 🙂
Oh, and I do not get anything from them for promoting them, but I have orderd many times from UK Tights which has a great selection and delivery is quick to the US. http://www.uktights.com. Don’t know if we are allowed to post stuff like this.