at that price, you're either going to have to make it yourself (raw materials cost about 3500-4000isk depending on the style you make), or hope that the salvation army store on Laugavegur has a cheap one.
The Red Cross Shop on Laugarvegur 12 has Lopapeysur from between 5000-10.000kr. There is also the fleemarket "Kolaporti冒" on the weekends, where you might find a cheap 2nd hand one (it takes a lot of looking, though).
