Re-evaluate your trip and why you need a food drop resupply. Although carrying 10+ days food may slow you down a bit, after half is eaten, you can do more miles. I have done 14 day trips without resupply. If you prefer lighter pack and going fast on the entire trip, then just build in a day to go to a trailhead or town for resupply. Horse packers generally are not allowed to just drop a resupply; they may be required to actually meet you, and most would not simply drop off food even if it was legal. Resupplies require precise trip planning and are expensive. I would rather have more flexibility and just walk out when needed or carry more food.
We had Fred Ross Lost Valley Packers do spot packing for fishing trips in the area years ago. They could take gear/food as far as steel bridge for a "one packer-day" charge. They stowed the stuff in 5 gal bucket so you don't have to meet them at drop off point. Of course, they may have a diff operation now. Beautiful areas up there.