How do I deal with this without hurting my wife's feelings?

It sounds silly, but this is about a pair of sunglasses. Expensive sunglasses, that my wife gave to me for our anniversary. The glasses were too small for my face and too tight to wear, so we had them exchanged for a larger pair of the same style that were specially ordered by the shopkeeper (our families know each other) as a favor to me. The new pair, though, is too big (I could really have used a size in between the first and second pair, but that size doesn't exist in this style or brand). I feel self-conscious wearing them and I'm beginning to make up reasons not to wear them. Returning them isn't an option for a couple of reasons, but mostly because my wife was excited about this gift, and I'd hate to disappoint her. How do I avoid wearing them without hurting her feelings or how do I deal with wearing something that makes me feel awkwardly uncomfortable?