Can you go to the shop with a laptop and plug mice from the exhibition? Some of the cheapest, most basic "ambidextrous" (marketing-happy way of not presenting "not profiled" as a negative) Microsofts or Logitechs are surprisingly good, as are bottom of the line A4-techs (which are even cheaper). All you need is to find the right one for your hand size and shape. The problem, however, is dpi, especially if you have a big screen. Dpi may limit you to "gaming" products, although there's plenty of noname or poor name 1200 and 1600 dpi optical or laser mice in the market. Some are rubber coated. Buttons may be a problem, especially in terms of drivers.
This said, there was a left-handed version of Razer's Deathadder, a big-sized, profiled, palm-gripping mouse. It might be worth looking at. Probably the closest to what you need. Perhaps within €30.
May want to look at this, though:
http://www.ttesports.com/products/product.aspx?s=14. Basic, no-nonsense mouse with rubber coating, braided cable and low friction movement.
Also look at
Steelseries Xai. Looks like millions of people have loved it over several years by now and it's used by a number of professional gamers (probably because of sponsorship reasons but anyway). It has high res (up to 5000 dpi or a bit more), it has additional buttons, it is huge, it has the coating etc. Depending on your subjective preference, it may turn out better than a specifically left-hand profiled mouse (for example I dislike most right-hand profiled mice).
By the way, you sure about palm grip? I used to be but I've found out that in many cases a small and light mouse will be less painful to operate than a huge palm-gripper, even with big hands.
