I haven't found unflavored instant oatmeal in little packets. I would skip the heavily sugared and artificially flavored ones (e.g. maple syrup etc.) in favor of the plain. I just pour a little of the plain oatmeal into a sandwich or ziploc bag and put in pocket. The instant oatmeal is already preprocessed so it's easy to chew as opposed to rawer steel-cut oatmeal.
The mayo packets are interesting idea. I just haven't found success mixing eating extra fat on days I exercise. My stomach doesn't like it.

It's probably anathema on this board, but I do best on a low-fat diet on the days with lots of hard exercise. On the days I'm recovering from muscle soreness, I go back to strict low carb.

This maybe bad advice to the person though who still has a lot of fat to lose like Rick51. It took me over a year to lose a bulk of my excess bodyfat, and during that time I was strictly low carb with almost no exercise, and that's when I really lost the bodyfat - at the expense of losing much of the muscle and fitness as well.
For Rick51, who is at 50%, of his bodyfat loss goal, it may be smart to accept diminished cycling performance and 'bonking' in order to lose the excess bodyfat more quickly?
It's really been a struggle for me to find good balance between losing bodyfat and gaining muscle mass and improving exercise performance.