Human lace wigs are a great idea. My budget does not accomodate those, so I do something similar. I use half wigs that are made of synthetic hair, but that have a super thin mono front. The Sensationelle brand makes some half wigs they call Instant Weave Lace Top... it has about half an inch of lace front material at the front edge. My personal fave is called Juniper. You can wear your hair all slicked back, with a thin headband over the demarcation and nobody will be able to tell.
In my experience, the half wigs that double as drawstrings have a thicker "lip", since the casing for the drawstring is under there. It's harder to disguise the demarcation for those. When I wear that type (I have tons of them) I take a normal wide elastic headband and fold it in half so that it looks like a narrow headband. The extra layer of headband fabric really helps to disguise the bump.
At the end of the day, most people are not scrutinizing you that tough... they are too worried about other folks seeing thier tracks, zits or whatever. If the wig is thick and relatively long, most sisters will assume it's not yours anyway... as evidenced by all the long haired LHCF posters who get accused of weaves/wigs even when they have thier own hair out.