Yes you can. Dahon seatposts 33.9 mm and are working for me.
https://xootr.com/collections/cleara...wift-seat-post Xootr site works for me. But you say your Swift is steel. Xootr Swifts are not steel They are aluminum and the diameter of the tubes are thinner AFAIK. You are warned to which you need. If you can't measure the diameter of your seat tube take it to a bike shop and ask them. Ask what frame is made of too. They have magnets. The front forks are all steel. Contact Xootr. They will steer you in the right direction.