Blast,
I own a machete, std. military issue, but I've never used it for hacking vines. In fact, any more, I never take it camping. Strike one.
There is a pretty nice one I like at Cabelas, but it costs more than $30. Strike two.
If you're interested, the Cabelas machete is $39, has a 17"-long slim blade and a Kydex sheath. # HG-51-5631.
They have another one that's $39. #HG-51-7381.