I am not from Laminar Research; just a flight simmer from downunder.
To make it very clear I am not a steam user and I do not support steam.
Steam is a 3rd party hybrid (modified) version of the official and original version of X-Plane created by Laminar Research. The LR version of XP does not and will not mix and match with steam. There is no commercial connection between LR and steam. Steam is taking a commercial advantage of the development work carried out by LR. The steam version has an installation process quite different to the official version of X-Plane.
If you know of a commercial outlet for the aircraft you are seeking then buy it. Laminar has stated in earlier postings in this forum they are concentrating on the development of x-plane software and have no further interest in creating new aircraft with the software. Laminar has a small team of developers and do not have the staff for aircraft.
As an alternative you may browse the following website found at www.X-Plane.org to ascertain if they have your aircraft. Although this site has no connection with Laminar they are a dedicate site just for X-Plane users.
Good luck in finding what you seek.