Harvest OUTB2000 HF/6M Mobile Antenna (80, 40, 30, 20, 17, 15, 12, 10, 6m)

A screwdriver antenna at least as effective for the same relative size, and has a much better bandwidth than anything the ISOTRONs advertise. Having a screwdriver antenna, I can attest that it's not a great DX'er, but it's better than nothing. ISOTRONS are not multiband, and they're pretty big compared to a coil loaded whip antenna. If you're looking for something small and cheap, here is a good option that I've been playing with for portable use.