Get a handlebar bag or a rack trunk and store your supplies in that. Look for a bag which detaches from the bike quickly and easily. If you also have a strap which hooks to the bag, you can carry it on your shoulder. This setup keeps the load on the bike when you're riding.

If the load is just a few small tools, there are some bags which fit under the saddle but detach quickly. Once the bike is locked up, it is a matter of a couple of seconds to remove these bags and carry them with you. Depending on the size of the bag, it is possible to carry all the gear except the pump, which can likely be mounted on your bike frame.

Another option is to use a small daypack if you can find a design which does not put pressure on your shoulders. The weight of the tools and patches and even a lock and a pump will be low. This method also allows you to transport a laptop or mobile device if you need to carry it with you. Carrying a load on your body is not as good as carrying it on the bike, but if the weight is kept low, this may be a workable solution.