I also carry a Chinese RH-770 in my backpack. It works fine on 2m, but is completely out of band on 70cm, maybe I was unlucky getting a bad one.
And as said above, it is a very delicate antenna, handle with care …
I have a flexible quarterwave on my FT1D all the time. The portable sits in a side pocket of my backpack (in it’s own padded bag), antenna fixed to the top of the backpack with a velcro strap. It sends APRS when I’m walking.
Search the usual shops for “Nagoya NA-771 Sma Male”.
This one is just an example, you may find it cheaper.
Results are a whole lot better than with the standard rubber duck, and a bit less than with the RH-770.
73,
Luc ON7DQ