"Thimbleberry, Salmonberry----lotsa names----Western Thimbleberry, Salmonberry, Mountain Sorrel, White Flowering Raspberry, Western Thimble Raspberry. You name it.
Relatively low elevations, only, though."
You've just given me an epiphany. Why not grow Thimbleberry in your backyard? For trips of only a few days, particularly at high altitudes, you just go out and 'pick' your TP before your trip. You get to bury your TP and don't have to spend an hour finding sutiable material.
Of course, with my complete lack of gardening skills, for all I know Thimbleberry uis an atrocious weed that will destroy my entire garden and spread to my neighbors. Better check with my Mother-in-law; I've had more than one humorous conversation with her--an Oregon native--where what I see as a beautiful flower (aka Scotch Broom, thistles), she laments and whips out the weed killers. But that's just my native so-cal eyes talking, where any sign of floral color whatsoever is considered a blessing! I've never had to uproot them before. She tells me that when they bought their 5-acre property, the entirety of it was covered in chest-high thistles and blackberries (bountiful berries and dazzling purple flowers, right?) =). Took them 5 years to get them to finally stop sprouting everywhere.