Trying to find a good 5 button or even 7 button mouse these days is pretty easy. Razer mice are by far some of the best that you can get on the market. They have great in depth dpi and the ability to customise each feature including but not limited to the flashing logo.
These mice can range from £30 - £60+ depending on where you shop for them.
However there are great cheaper alternates on Ebay which you can import from countries such as China, Hong Kong (these being the main two) etc.
For example if you search "5 button mouse" within the mice category of Ebay. You can browse through yourself on either the auction tab or the buy it now. you may also change the search criteria to 6 or 7 button mouse to a greater selection.
I would recommend looking at "Top-Tech-Ltd" (sorted lowest to highest including P&P) shop range as they have a very good selection starting from as low as £5.95; their most expensive (currently of posting this post) is £29.99. Therefore far cheaper than Razer.
However when it arrives you may find that the 'Back' and 'Forward' buttons are the wrong way around. In which case you can fix this by downloading and running X-Mouse Button Control. This program is fantastic and allows you to customise the buttons on your mouse.
I personally bought the '7D Cruiser Transformer 2 II USB'. It's smaller than I thought it was but the quality is fantastic.
Hope you found this helpful in making a choice and saving yourself a lot of cash!