I am trying to find a power cord for my laptop, but each one that I find has the output which is what my input is, so I am not sure how to find a power cord for it. I have a
Compaq Presario 900 US, my Input Rating is 18.5V DC 3.5A. The cords I find have an Output of 18.5V 3.5A, how do I find the right one?

Here 'ya go:
Compaq Presario 900 ac adapter - $31 (http://www.simplemicro.com/ppc/goog/presario-900-ac-adapter-g.html&campaign=goppc&kw=Presario+900+cord?gclid=CK3TiZSpvJQCFQKcFQodRDR bTw)

ComputerLogin :: 90W AC Adapter for Emachine HP Compaq Laptop = $30 (http://computerlogin.com/sales/productfilePHP/Y_Emachine_4_9A.php)

Power Cord Charger Compaq Presario 900 900LA 900US 901 - eBay - $27 (http://cgi.ebay.com/Power-Cord-Charger-Compaq-Presario-900-900LA-900US-901_W0QQitemZ180260899625QQcmdZViewItem?IMSfp=TL08 07041469r39851)