The tie rod is a form of turnbuckle. 1/4" heim joint ball ends are used. One Heim joint per end of turnbuckle. On end of turnbuckle is right hand thread, the other end is left hand thread. So one heim joint is 1/4" right hand thread and one is 1/4" left hand thread. Since your bicycle is a SWB your turnbuckle wont be that long. Steinjager makes both aluminum and steel turnbuckles in many lengths that would span the distance from your handlebar to the front fork. My Ryan has a tab welded on the fork crown that accepts the front heim joint. The handlebar can be as simple as a bolt and nut with nylon washers providing the bearing surfaces drilled through a suitably bent aluminum pipe and mounted under your seat front with some sort of frame clamp. If you see a Ryan Vanguard or Linear you will see this entire system and help you design/build an underseat steering system. Linear Recumbents/Bicycle Man LLC has handlebar ends that would really help and may have other parts also. Query Steinjager on the internet. I bought some new 1/4" heim joints for my Ryan seat back supports recently from Speedway motors. They sell them as part of throttle controls. Good luck.