Replace / Repair Diamondback bike stem I have a Diamondback Edgewood 26" hybrid bike.  I believe it is a 2008 model.  Mostly it's a great bike and it certainly serves my needs right now.

However,  the stem has become loose so the handlebars pivot on about a 75° axis.  Thus, the only way to ride it is to tilt it forward so it is flat - definitely not the most comfortable position.

The top and bottom screws are adjustable, but they don't effect this aspect of control.  The side screws are what I need to adjust - 4mm hex screws on both sides - and completely stripped.  If they made a 4.25 - 4.5mm hex bit, I might be able to get it out, but I don't think so.  It's pretty rounded.

So I'm probably gonna have to drill them out, and my question is twofold:


Can I replace just the screws - if so, with what?  How to know correct measurements?
Or failing that, is the stem replaceable and where can I find the right one?  I looked around  online, but I couldn't find anything that I was confident would be an answer to my question.
From the information available your bike uses a 1-1/8" quill style adjustable stem. The only other pertinent  variable is handlebar diameter. While you most likely have 25.4mm (1 inch) bars you could have 31.8mm bars. Locating replacement bolts will likely be difficult as the pinch bolts of pivoting stems are typically brand specific in terms of length of the shoulder and diameter of the head.