I always liked the Miracle Whip / Wonder Wand type of QRP antenna’s but could never stomach the price. So, I just built my own to use with my FT-817.
The antenna is a 6′ telescopic antenna from an old CB and the case is the cover/protector for my car stereo removable faceplate. The inductor and position switch were just a used toroid and a used 12 position switch I had around. It works very well and provides a decent match on most bands without fuss. You can see it in use here on YouTube.
I must say that it is mostly a dummy load. While I have had a few decent QSO’s using this setup it’s less than great. Another reason I’m glad I built it rather than bought it. I can tell you that a ground (counterpoise) is essential to using this type of antenna.