Hi Becky!
Thank you for bringing your question to the Disney Parks Moms Panel!
I am sorry they sold out while you were researching! Those jackets are always very popular. Generally, they will not be available for pre-sale again before the race weekend. There will be some available at the Health and Fitness Expo, but those sell out fairly quickly, too. You can definitely keep checking the
Princess Half Marathon Registration page to see if more pre-orders have opened up.
I will say that during the past few race weekends I have attended, runDisney has done a much better job at spreading out the merchandise and allowing those who get there on day two of the expo to find some of the hard-to-get items. In addition to the jacket you can pre-order, there will be more jackets to choose from. Each race weekend always has some really cute items and the jackets are usually near the top of my favorites list.
I am not aware of any size charts, but I find the jackets to run a bit small. I always buy a size up to allow for any shirts that I may have on underneath it and I like mine to fit a little bit longer. I have never actually pre-ordered a jacket because I like to try one on before spending that much on it.
I hope this helps! Please let me know if you have any other questions.