I have the Fly Trap, but found it kind of heavy so only use it on my canoe bag. I did have to replace the foam so far. On my two chest packs I now use a C&F flypatch. Flies go into the slots butt first, so even barless hooks hold firm.
I also have a Streamworks which has a clip to put on your shirt (no holes) or a 'dog collar' clip. It is OK too.
And you can always take an old film container or pill tube, drill holes in is (and one in the top) and run an old piece of line though all so they don't get lost and pin it to your shirt or vest.
I agree that the dashboard of the car is a good place to dry out all flies on the ride home (keep them in the fly patch not loose!).