I wouldn't use nail polish but that's just me, I would stick to tape. If you wanted a more permanent fix, Illumnation supplies sell pre-cut shrink wrap. Just peel off the old, put the new over it and use a hair drier to get the shrink wrap nice and tight.
Edit: When you put your batteries in the sigelei, try to keep them level rather than letting 1 side drop in before pushing the other one in. I have the 150 and I noticed it was hard to get the batteries in if 1 side was already in, so I backed it up and pushed both sides of the batteries in at the same time. Little indentation marks on the wrapper but no scratches.