I have had problems with finding things to fit Jade too, everything is just too tight in the chest to where she can't walk comfortably. Sweatshirts get tight across the arms and jackets with just velcro straps don't cross her chest enough, they either come undone or there too tight.
Well tonight I was at Petsmart and my daughter brought me this jacket that velcroed under the belly and across the chest, like other ones I've tried but don't work well, but she insisted that I try it on Jade (she loves to find things to put on the dogs) so to show her that they don't work I put it on and to my surprise it fit her perfect. I was amazed and even though I had no intention on buying another coat (cuz my hubbie thinks I'm nuts with all the clothes she has) I couldn't leave without it.
I wanted to let everyone know about it because I know it's not often that we find things to fit our boxers, so if you have a Petsmart maybe you can look for the same one. The brand is Companion Road, it's just for Petsmart stores. The tag calls it a 'Toggle coat', it's biege and looks like a suede leather with fur on the inside and around the collar. At my Petsmart it was $20 (not bad)