The best place to carry small items on the bike and have quick access is the top tube. This has discovered first of all the triathletes who used top tube bags for your gels, etc..
This bag has nothing to do with triathlon. But it offers the perfect storage for everything possible during your bike tour: phone, wallet, bar, but also an extra power bank for the light or for the bike computer on extra long tours.
The bag is attached with two screws on the top tube. Provided that your frame has, as currently many all-road and gravel bikes, appropriate attachments provided. (If not, there is also a top tube bag with strap attachment).
The bag is made of a three-layer laminate, has welded seams and is therefore waterproof. Which also applies to the zipper. On the bottom it is so well padded that even edged objects do not damage the frame. And in the front a small opening ensures that a charging cable can be led to the light, to the computer.