Can't you use readymade? We use the SMA bottles and they are 250ml so divide easiily into two 125ml feeds. You could also take a small flask of boiling water and there are plastic container things you can pre-measure doses of formula into.
I take a flask of water with me when out and about, a sterilised bottle, and the formula pre measured. It's a bit of a faff, but having the water pre prepared in a bottle isn't the best way forward, as the water needs to be hot when the formula is added, to get rid of any bacteria in the powder.
Guidelines for if making up the feed fresh is not possible are to make it up at home, cool quickly (so in iced water or something) and then to us within a certain time- I think it is 4 hours but don't quote me on that you'd have to check. What to do if you are going out for longer I don't know! Use cartons I suppose, except that creates a heck of a lot of waste until they are drinking that much.
I'm pregnant with DC4 who has a cleft lip (not sure about palate yet) and probably low muscle tone as well. With the others I've mostly breastfed but also done expressing, NG tube feeding and did a 2 week trial of feeding DS3 allergy free formula to see if it helped his reflux (it didn't).
Anyway, I'm trying to work out my options with feeding DC4. I'd much rather breastfeed given the choice but if he/she can't I need to do something else. Whatever happens I'll be trying to breastfeed and if he can't breastfeed I'll be trying to latch him on while pouring EBM/formula into his mouth via the supplemental nursing system or NG tube so that he knows that boob = milk and hopefully we will be able to breastfeed post surgery if we can't before.
People keep telling me that FF is so much easier than expressing but when I did it I thought expressing was easier. I could always get at least 6oz in 20 mins and could keep it in the fridge or in a cool bag when out. With FF I made up each bottle when DS3 needed it which meant I couldn't go out anywhere unless there was a kettle where we were going and a way of cooling it down quickly. Was I doing the FF wrong? Most mums at baby groups had pre filled bottles of water and added the formula when needed but I thought that was against the guidelines.