Altus sleeved poncho is somewhat heavy at .5 kg (17.6 ounces) but just 28 euros.
A lighter, but more expensive, alternative is a packa:
http://www.thepacka.com/I have never used either. I prefer a good, lightweight rain parka when it is cold when i might depend on it for warmth. But, I still prefer a good, lightweight poncho in summer conditions, especially the one from Integral Designs, a Canadian company and the most innovative developer of lightweight backpacking products I have ever seen:
http://www.integraldesigns.com/product_ ... cttypeid=1this costs less and weighs less at 10 ounces (280 g) and you can use it as a tarp and sleep under it. I have used one of these now for almost 10 years.
Alternatively, with a small pack, as some use on the Camino, look at their 5 oz rain cape:
http://www.integraldesigns.com/product_ ... cttypeid=1