I did this with an old pair of SKS fenders:
Get a scrap pair of fenders from the LBS, cut a section to the length you need, pop-rivet that sucker on the front fender.
For clearance reasons, rivet them "heads in" and use a rivet washer on the outside to keep it from pulling through. You can use a tack hammer to round over the visible side of the rivet if it much matters to you.