Aber hollo seems to be offset towards the center,
and may come in close enough to work..

center sleeve type bars, Nitto, and such would do well.

alternative With Ergon's longest GP 5 on a straight bar
the integrated wide surface grip and bar end
there are almost many as many hand holds..

The whole steering riser mast comes out
and can be changed.. can't it.. ?

IDK, just have a BiFri PL , a Brompton
and several regular big wheel bikes.

but the folders both have a threaded headset,
and the steering mast has a quill to secure it into the fork,
the bolt, which is accessed when the hinge is folded.

$130 ITM 2 piece and,very adjustable Modolo Dumbo,
made 3 U shaped pieces, 1, 25.4,.. 2, 22.2..
with clamping pieces to join them .. were available..

SJS was carrying the Modolo, I got an ITM one from Wall bike,
but they are gone too.

I might sell mine, I played with an aero bar mix, on it for a while .