Here is an example of an adjustable stem.
http://aebike.com/page.cfm?PageID=30...ils&sku=SM2081
The links I have mentioned all come from aebike.com who's catalog is basically just the QBP catalog. QBP is a distributer of bicycle parts that nearly all bike shops order from. Your LBS should have a QBP catalog and be able to order any of these stems.
I perfer a high rise stem over a stem extension or an adjustable stem because it is simplier and should be stronger and have less flex.
Craig