Ruben I’ve run into this same issue. I use an off trail route on Green Mountain in Boulder. See the attachment… it can be extended farther to the summit of Green but as Josh said you probably aren’t going to find an actual trail outside of the incline in Manitou. Word of caution with any of these off trail routes please be respectful of the environment and follow practices to minimize your impact to the area, especially as some of these very steep areas are also very erosion prone. The route below is almost entirely on forest duff which is some of the better stuff to be stomping around on.