I have a 2009 Dahon Speed TR, This is a great bike that I was inspired to buy from reading the enthusiastic folder fanatics on this forum. My other bikes have drop bars. One of the things that keeps me from riding the Dahon for long miles is the lack of hand positions. A good compormise seems to be to put some trekking bars (butterfly bars) like these:

(image borrowed from Nashbar)

The raised center section is 1 inch dia. ( but less so to the left and right)

I have this kind of stem clamp on my Dahon:
(image borrowed from thorusa)

Which clamps a 1 inch diameter bar on the sides of the raised center section.
What to do?
Can you advise me on a bar that is uniform dia. across the clamp area? or other solution. Thx in advance.

From Thor's site either the Aber Hallo or the revolve stem with quick release?
https://www.thorusa.com/accessories/handlebar.htm

Also look at the Soma Sparrow and the Satori Vienna bars on Thors site before deciding https://www.thorusa.com/accessories/handlebar.htm

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 .

The Soma and Satori appear to have a raised center section and do not seem applicable to the stem type I have.

It appears Dahon Radius 5 extender and the revolve stem would allow the installation of Trekking bars (or many other standard handlebars). This solution is a little pricey for my budget ( over $100 not including new bars). I really like this solution but would have to wait to try this.

The Nitto Trekking bars seem to have the same raised center like other trekking bars. They do not have a sleeved center section as their road bars.

The Modelo Dumbolook very cool and seem extremely adjustable but they are outside my budget for this project.

I will post pics back if I can decide on the best solution for my budget and desires. Thanks very much for your inputs.