Transparent Mesh with no Texture?

Are you sure the item isn't borrowing textures from another item? Because that one doesn't look like it has textures included.

I'm guessing that it would be the same process as adding a cutout to a sink. I just tried it on a cloned items which I erased the dst image and created a new one, and it seeems to work  

- Open the original sleeping bag and export the texture
- Open your custom item
- Use Hash generator to create instance number
- Go to warehouse and click on add > DST image resource
- Paste the instance number you created and change group with 80000000
- Import your original texture on your new DST entry
- In the warehouse, click on Model LOD > Edit items... 
- Select phong or wathever shader it uses > click on Resource > Entries > Edit Items...
- Then for each variant, click on materials > Items > Edit items and on diffuse map, paste your instance number and group
- Go back to the warehouse and click on model > Lods > Edit items ... > and then select medium. On the right, Meshes > Edit items... and redo the previous steps for the medium and low lod.

And voilà It won't appears right away, just click on "Add swatch" so the new texture shows. Let me know if that works for you