I know of something you might try
I am happy for you that your wife embraces your femininity. Far too many people on this forum are not so fortunate. I, too wear only nightgowns to bed. In fact, my wife and I wear the identical model and I LOVE everything that represents. After much trial and error in buying from eBay, I found my perfect nightie - Silk Essence by Miss Elaine. There are no spaghetti straps and the Antron fabric has a fair bit of stretch so that it moves with you as you sleep. Whenever I wore something satin, the fabric tended to get pulled tight here or there, waking me up more often. My Miss Elaine lets me sleep in total comfort. (There are also plenty of on line retailers)