Coco coir and fine grade orchid bark can both be found cheaply in bulk at local garden centers. OSH, sometime carries o bark, but most hardware stores don't. Sometimes its also called "fir bark".
Bought-in-a-bag soil should never be used as substrate for a tortoise, too many additives, and my main complaint is that you can't know what composted material it is made of. Is it chemically treated grass clippings? Oleander and azalea trimmings? Maybe it was something safe? No way to know. I once got a batch for one of my above ground planters, and there was there were obvious jacaranda leaves in it that had not fully composted yet. Jacaranda is toxic. It could have been a disaster if I'd put that into a tortoise enclosure with a baby.
