Laci LeBeau Super Dieter's Tea is what I use.
I use it because it works well for me. I think I got it from www.drugstore.com. It comes in at least a few different flavors. It seems that most folks around here use Smooth Move. I bought some (chocolate - just because I like chocolate), didn't really like the taste afterall - or the cramping. I was able to find it at my local Heqalth Food Store.
Cleansing of your body through tea is a good idea! Talking about Senna tea for detox - Senna tea is normally made from Cassia Sena herb. But there are controversies on it's consumption.
Also, it is not easily available in the market.
I would suggest you to try green tea, as it is world wide accepted as a refreshing & detox herbal tea. Green tea is a natural flush for your system, antioxidant-rich, also drinking green tea will not only help your body increase the production of detoxification properties but also increase your immune system and protect your liver!
Drink one tea cup of green tea early in the morning and 9 hours before you sleep for almost 30 days, it will surely help you detox your body as well as keep you refreshed.
About the brand, as you haven't mentioned your location, I would suggest to buy tea from Goodricke Tea. They have vast tea gardens which are one of the oldest in South-Asia. They deliver globally and the quality of green tea is premium & very refreshing.