Reddit reviews Super Power Supply AC / DC Adapter Charger Cord for 12V 5A 5000mA Netgear WNDR3700 WNDR4500 R6300 AC1450 R6250 D6200 Centria N900 R6200 R6100 N600 LCD Monitor LED strip AD-LCD12 FP450 FP547 FP553 FP557 FP563 FP567 FP581 FP581 FP591 FP731 Benq Wall Plug
We found 1 Reddit comments about Super Power Supply AC / DC Adapter Charger Cord for 12V 5A 5000mA Netgear WNDR3700 WNDR4500 R6300 AC1450 R6250 D6200 Centria N900 R6200 R6100 N600 LCD Monitor LED strip AD-LCD12 FP450 FP547 FP553 FP557 FP563 FP567 FP581 FP581 FP591 FP731 Benq Wall Plug. Here are the top ones, ranked by their Reddit score.
Input: 110-220V Output: 12V .5AWarranty: 1 YearSuper Power Supply are manufactured and tested to match or exceed OEM products.Trademarked by Super Power Supply. Sold exclusively by Super Power Supply
It is somewhat uncommon for companies to carry spare parts for consumer level equipment, it really is not worth them inventorying and manufacturing extras in the instance that somebody may need one for what is a "cheap" router. I know that over $100, is not considered cheap to many, but in the router world, it is.
A quick google search turned up this http://www.amazon.com/Super-Power-Supply%C2%AE-WNDR3700-WNDR4500/dp/B00EV5W670
I think that is what you are looking for.