If you're using the attic enough to be concerned then
the only right way to do it is to put the wire under the floor,
through the joists or stapled. Either way it should be
as close to mid-joist as possible. (It's apparently legal
to run it on top of the ceiling below, under the joists, but
that's not really safe. Someone might decide to hang
something from that ceiling.)
It shouldn't be covered in a way that hides the romex but
still allows a nail or sharp object to go through and pierce it.
A rubber cover that can be stepped on can also allow for
rubbing. That's not a big risk, but I remember one case some
years ago in Cambridge, MA. A handyman ran romex under a
carpet. The romex wore through. The house burned down.
People died. The handyman was charged with manslaughter.

Another method would be pipe conduit. It's not terribly
expensive. I expect you'd pay more for a thick piece or
rubber. But you might need to add one or more junction boxes,
depending on where the end o the wire is.

"FTR" wrote in message
...
I have unfinished attic space that I used for storage. I have a plywood
floor up there, and there's romex running along the floor.

I want to protect the romex from people walking on it / stuff leaning or
rubbing on it/ etc.

Does anybody have any suggestions about what to use? It needs to be
something that I put right over it, and staple down to the plywood so
conduit it not going to work. I thought about using some wire moulding but
it's kinda expensive and I need about 30 feet of it.

Is there some rubber product that would work in this application?