I guess you could try AmiFig. It's not too bad for a structured drawing/vector art program, and it's been updated more recently than any of the old 68k software. It's available for OS4, Aros and an older version for MorphOS. You can download it here:
http://www.os4depot.net/index.php?function=showfile&file=graphics/edit/amifig.lhaAlthough I don't know how well you would go exporting graphics to another platform, but at least it's free so it's worth a try!
Here is a demonstration of the OS4 version:
[YOUTUBE]6fIW_6YZiJ8[/YOUTUBE]
And a demonstration of the Aros version:
[YOUTUBE]fjq8ct5d5IY[/YOUTUBE]