We purchased ours online at doorsuperstore.com. Great quality, good price. I also talked with the guy at manorhousedoors.com when I didn't think we were going to get our door in time (due to hurricane in TX), and he had excellent customer service and a nice price as well (he was willing to price match -- plus he answered the phone after hours).
If you don't feel comfortable ordering online, your lumber supply house probably carries some, then there is always the big box stores...
GL :o)
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Darker garage door, walnut entry
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