The grade one spell books are available as printables for 18" dolls in several places on the web. I got mine from the Wren*Feathers blog: https://jenwrenne.wordpress.com/?s=Spell+books
Around the end of September or early in October, the Christmas ornaments started to appear on the store shelves. I had seen a number of owls, but most were either too big, or too small. One day I was shopping in Michael's, and spotted a white owl, shown along with some other woodland type of ornaments. While it was not a dead ringer for Hedwig, as the feathers were accented with a pale brown instead of black, it looked to be the perfect scale, so I purchased one for Harry. (Frankly, the slight difference in coloring has never seemed to bother either of us much.) Some time after that, I found a bird-cage type of candle holder in the Family Dollar store. I whipped the tape measure out of my purse to make sure it wasn't too small. It turned out to be just right, and voila, Hedwig had a cage! She now sits cozily perched in the round metal spot meant to hold a tea light.
I made Harry's shirt from a personal pattern that I had designed a while back, and have made frequently in both long and short sleeve styles. (Harry's navy frog shirt is made from the same pattern.) There are a number of similar patterns available, including a dress shirt pattern with sleeve and collar variations from the "Sixty Sewing Patterns to Fit Sasha and Gregor From Marcy Street Doll Company" pattern book, by Ann Louise Chandler. (It is now out of print, but sometimes the booklet, or the original Marcy Street patterns come up for bid on eBay.) Another of my favorites is pattern #131 - Shirt with Yoke and Sleeve Variations from Denise Ortakales of "The Doll Carriage", (which also come up for bid on eBay every now and then,) and the last of my favorites is the shirt from Evalyn Styles' Brownie Jumper and Blouse, from the Winter 2003 issue of Friends of Sasha newsletter. (The 2003 four issue set *may* still be available from Dorisanne Osborn.) There are other shirt patterns available as well. Judi Arrington sells lovely patterns with a very nice fit on her website: http://designsbyjudi.angelfire.com/Sasha/SashaCat.html
Harry's pants are made of lightweight gray wool gabardine, from a pants pattern that was published in Friends of Sasha. Mine has a front opening mock fly, but that detail really doesn't matter, as the sweater covers the front of the pants anyway. When I made the swap outfit for Henry, I made the tie of a lightweight satin fabric, and sewed on the contrasting ribbon stripes. However, for Harry's uniform tie, I simply cut a piece of scarlet grosgrain ribbon for the tie and cut it to a point at the ends, stabilizing the edges with FrayChek. I intend to paint stripes on it using a gold paint pen, when I get around to doing that.
I had been looking for a trunk for some time, when I finally found one at Hobby Lobby that I thought was large enough to hold Harry's wardrobe, but not so large that it looked ridiculous. One of the last things I put in his trunk before he and I set off for the August 2016 Club meeting, where our wardrobe challenges were to be revealed, was his plain pointed wizard hat, which all the students are shown wearing in the scene of the Sorcerer's Stone movie where Professor Dumbledore awards the House Cup. I just cut a cone shape of black wool felt, seamed it up the back, turned it right side out and plunked it onto his head! Below is a photo of Harry's trunk, wardrobe, and accessories, as of August, 2016.
I have continued to work on both Harry and his wardrobe, and have several things that are not pictured above. I found some hair that was a good match for his color and started re-rooting the back of his head this past winter. It's coming along well, especially since I now have a rooting tool of sorts. I'll try to get a photo of his current set very soon and update it here on the blog. There are still a number of items on my list that I haven't yet made or found, but the journey is where much of the fun lies. I look forward to playing in Harry's magical world for a good while longer!