I dont know your location but moss is a fairly abundant resource (in small amounts) in most of the USA. Look in a partly shady area under some trees, or in swampy area's, Your likely to find some
Moss is great stuff becouse it has anti-microbial property's yet retains many beneficial fungi. Even standard milled peatmoss is good in small amounts, When I use something like mostly pearlite/vermiculite a very light coating of milled peatmoss can help avoid some possible issues.
It even works as a primitive wound dressing, as well as water sanitation agent in a pinch (educational only user beware !!) Becouse it contains a good amount of Iodine, which is beneficial to human health in a number of ways, mineral, blocks certain forms of radiation uptake ect. . (Sorry I love moss)
I would be concerned about rot/molds with shredded paper. In my opinion coarse sand would be better than paper. But then again my strike rate with psycotria is not good.