I'm pretty sure demin can be dyed normally. Use liquid dye in a tub and let it sit for a while (obviously mixing it around a bit every once in a while, maybe every hour, and leave it in for a good half a day for a deep nice red that's void of pink hues.
You can get white ones in places like motorcycle/biker clothing shops. Or try places in the mall like macy's and the sort. Though those places will be REALLY hard. More because it's becoming summer, so heavy coats are leaving the shelves, which is why I say biker clothes shops, because they have that stuff year round, but it costs a lot more..You can try different thrift shops too. As for Iron on stuff or whatever, I don't exactly know what it looks like so I can't help there, but if it has like the Umbrella Corp. logo and such, then you can get iron on ones at hot topic for pretty cheap