I am so sorry about your bf'ing difficulties!
With powdered formula you can get those little things you can take with you... Like these, but they have similar ones at Target (safe plastic, too).http://www.safeandsecurebaby.com/Pow...in-pr-521.html
I used to keep bottled water in my car to use for on the go bottles. You can also get the RTF bottles to have on hand for emergencies. (Ready To Feed.) I've also filled up the bottle with whatever water I am using, and take that with me, then dump the formula in later. I have had to heat the water in advance, too, my girl is picky and won't take cold formula.
After a certain age it is fine to use tap water instead of boiled/sterile water. Dr. Sears has a good resource on bottlefeeding formula; I hadn't done ANY research when I had to supplement my daughter!http://www.askdrsears.com/html/0/T000100.asp
Now I just want to throw this out there and say that IF you would like to, you *can* maintain a nursing relationship with your child, even if most of her nutrition comes from formula. That is what I wound up doing, and my daughter is 20 months and still nurses for comfort. If you aren't interested in that, please don't take my saying this as a "you should." You should only do what is best for *your* family!
I highly recommend MOBI for support and it is an excellent resource, no matter what path you follow at this point. http://www.mobimotherhood.org
. No one there will try to convince you to breastfeed or make you feel like you haven't done enough. It is a wonderful group!
I hope you find some of this helpful, I am so sorry you are going through this mama!