My thoughts are that is a small lathe, extremely unlikely to turn anything that needs a steady rest, so high probability that like many of us you want to make one, will use it twice and decide it is a fiddle too far, and put it on a shelf as a workshop ornament, like I have!
Those factors considered you have a wood lathe, probably have a method of sawing timber too... take off the banjo measure it and draw round it then copy that design in timber to make a timber clamp base for your steady rest, it will be strong enough to use, and plenty strong enough to gather dust after :-) most important thing is you made it!