I agree with zebedeethezebra. I fully intended to breastfeed and resisted my mother buying me bottles 'just in case'. My newborn cried all the time from birth, fell asleep at the breast and behaved strangely - latching on and off, head bobbing. We had the midwife round time and again, and she just said it was breastfeeding technique, despite baby showing this strange behaviour when she was present. The midwife even said it was a shame to express, even when it would take 15 minutes for baby to latch on! We were supposed to see a breastfeeding consultant who never turned up.
To cut a long story short, we ended up in the neonatal intensive care unit when baby lost 13% of her weight and eventually had enough and refused to breastfeed (five days after birth). I wish I hadn't believed the breastfeeding indoctrination of antenatal classes, where they said everyone can breastfeed. I have polycystic ovarian syndrome, and it turns out that I didn't develop the breast tissue to breastfeed - I just don't have the supply. As for the stomach the size of a walnut, they say that in antenatal classes, and that's what made me think she was getting enough, when she wasn't. When we went to neonatal intensive care, five days after birth, she was on 55ml of my expressed breast milk and formula every three hours. We were there for three days while she got near her birth weight again. Mine is an extreme story, and breastfeeding works OK for most people. However, in the hospital they said four in ten women have problems with breastfeeding. Most of the early returns to hospital were said to be due to feeding problems - including milk coming in late. They hospital doctors also exploded the myth about nipple confusion after using bottles - they said it just isn't correct. So if you have to top up, do so and don't worry, or your baby will go hungry like mine because I felt I shouldn't use formula or I'd failed.
You can get bottles in most big 24 hour supermarkets. I would recommend the 125ml ones with slow flow one hole teats, which is all newborns can take. If you live near a big supermarket then just wait to see how you get on. If you don't, you could buy some in case and then sell them on if you need to. The formula boxes say how much to give for the age. You won't find an independent evaluation of formula - no-one will tell you what is best because apparently it is 'advertising'.
Hope this helps. I hope you get on OK with breastfeeding.