Uh, they still make thread-on pegs. You guys need to get out more.
There's the narrow cheap ones which thread 26tpi on one side and 24tpi on the other, depending on whether you have a freewheel or coaster brake, and there's big stocky ones that
AFAIK just come in threading for freewheel axles.
But yeah your axles aren't meant to carry the weight of a young adult on pegs, but that's been said a million times already.