[northNH]

"but location looks a bit tacky..." Certainly compared to the '68-on cheapish plastic brake lite housing on the left, I think not...

"...and requires chopping a hole in the dash.", but only if you don't sequentially use some appropriately sized drill bits, or hole saw bit, or one that's close and a good round chainsaw file and patience.

ALL factory flasher switch installs retain the lighter in its original ideal location.
And I think Volvo's factory-installed location for the flasher, above the fan switch, was the result of a long series of productive engineering meetings, and I think they got it right.

It takes less time to install a fuse into the lighter circuit than it does to wash the car nicely...

Also worth noting that after '64, in their Accessory Catalogue, Volvo made available functionally identical (to post-'67) 4way flasher units with a chrome knurled knob and integral dark red indicator light that mounted on its own little panel from the bottom of the dash to the left of the wheel.
From the catalogue--"Flasher system WILL operate even when ignition is turned off! $8.95"
This is the one that would be "period-correct" for a pre-'68 car, if that mattered to anyone.

I've got one of those nice old fellas rattling around here somewhere, and several of the later Amazon and 140 ones, which can be slightly different, and are real easy to find 'cause they last forever and they made several hundred thousand.

And what Ron said...