A couple of thoughts on lack of convenient foods. If you are going to be out for awhile, eat a fat-heavy meal and you will likely stay satiated all day: Yesterday I had a piece of fat from the corned beef I prepared to finish the meal, maybe 3" by 3" and felt like I was stuffed for a few hours after. So that avoids the issue.
If I want to have a snack handy I have a couple of things I use. One, there are always nuts and a few go a long way, I'm careful not to overconsume. For variety I will sometimes combine nuts, unsweetened coconut flakes and perhaps cut up pieces of jerky. For the jerky it can be tough to find it without sugar so be careful. Again a little goes a long ways especially if you had a fat-heavy meal beforehand. (For breakfast, I will make an omelet with two or three eggs, veggies, perhaps bacon and cooked in plenty of butter or bacon grease. Easily gets me through a day)