Easiest to make portable 2m/70cm antenna?

A 2m coax vertical dipole would work.
Strip the outer insulation off of about 19.5". DO NOT cut the braid.
Fold the braid back down over the remaining coax.
You can leave or uncover the center conductor .... don't really matter.
Adjust the lengths for frequency and swr.
Attach a solder lug or loop of some sort to hang it up.

Congrats! you just built a vertical bazooka.

 

I made a SO239 GP for my first 2 M FM experience. It was stuck on a piece of thinwall conduit on an old TV chimney mount and stayed there for about 5 years until I got a slightly Better 5/8 wave, factory made, vertical GP antenna.
<<The QW GP for 2M is a 3/4 Wave on 440 MHz and will work with low SWR and just slightly less low angle launch toward the horizon.>>
That first GP really worked ! With 25 W output I could work Mobiles over most of the metro area on simplex.
Back then we used 146.94 as the main Simplex channel, That sure dates me

 

With a bit of ingenuity, a 2 Meter vertical can ALSO work on 70 cm! Not the best on either band (depending upon actual used frequencies) but I use a 2M 5 el. Yagi on 70 cm with acceptable SWR on both bands. The radiation pattern, however, on both bands may well be a bit skewed.

 

ZGZ - A vertical -bazooka-? I don't think so. A vertical dipole, yes.

 

If you make the spacing similar to 'ladder line', it should work fine. I'd build it a tad larger than what is 'normal' for ladder line, then trim for best results.
Remember the giant candy filled 'canes' you find around Christmas? The big ones are something like 4 - 5 feet tall. Glue wire along the sides to make a sort-of 'J'-pole. Eat the candy first!
Same sort of thing can be done with 1.5" - 2" PVC pipe. Any insulator that's long enough and the correct (close) diameter.
How about a three bay candy-cane vertical array?! If asked, tell neighbors it's a Christmas decoration and the lights burned out...

 

build sumpin fer two, it will workon 450!