You might look for some used dura-lite rims.
They were 3 piece and not very expensive back in the '80s, many Solo2 and road racers ran them.
A common size was 16"x10"
I used a set of 16x10 stock car style wheels for years on my time trial car, they are very heavy if it matters!
Try Circle, or Diamond, they may still make 'em.
But yeah, if you can't find any cheap 16s, 18s are the way to go!
And almost anything will work better than those T/As!