Shielding can work better given an external energy source. If you can travel shamanically, find a plentiful source of ambient energy and plant an absorption construct with a cord to your shield, then program the shield to take from the construct (you can program yourself as a backup if needed). If you do this shamanically, the cord should require minimal energy to install, as geographic distance is inconsequential. Placing a cord astrally wouldn’t be worth the energy unless it’s very close.
The best source I’ve found is above a rainforest, teeming with rich ambient energy. Remember, this is feeding your shield, not you (although you can use it as such). The shield’s energy needs don’t have to match your own, e.g. I find most plant prana distasteful, but shields and other constructs don’t care. Instruct your absorption construct to drain only ambience, to ignore any actual organisms. Also remember to give it a reasonable end date, such as “upon my physical death,” and tell it to drain only enough for the shield.
Some shielding hints: Standard, unidimensional shields are notoriously poor for blocking tendrils. Rather than attempt constant multiphased or invulnerable shielding, learn to notice when someone is draining you and pull the tendril. Be careful of defense mechanisms, such as hooks or claws. Most of these mechanisms are instinctive and the person/entity draining you is unlikely to know they’re doing it. Just visualize the impacted part of your energy body phasing to a different frequency than the tendril and gently pull it out when safe. Sometimes it also helps to shoot your own tendril into the center of a hooked/clawed tendril, which may force the hooks to release.