This is an easy one! Window4U is your man. Awesome guy, best products, fair price. Find him on this thread: viewtopic.php?f=1&t=5035
...just click the Get a Quote button next to his name.
...btw, Felco's windows are made by Thermal Industries. Mediocre and outdated product. For comparison, you want to pay very close attention to the thermal and structural ratings as opposed to the sales "gimmicks" that everyone will throw at you. You also want a welded, sloped sill. The only time that pocket sills (like Feldco and others) are acceptable is in coastal applications where they can be necessary to meet requirements.