I'll just point out that the turtle module in pythonista is written in pure python (plus the canvas or ui module, I forget which), so can be edited to provide whatever missing functionality you need... Although that may be more effort than you really want!
For instance, see
The cpython turtle module is mostly NOT tkinter -- in theory it shouldn't be too hard to just strip out the tkinter drawing methods with ui.path drawing methods.
If you are trying required to submit programs that work in a particular environment, you probably should make sure that you run your final checks in that
environment -- get yourself a free shell account if you don't have a desktop/laptop. Sagecell also is a way that you can run code in a more standard environment (there are some threads on pythonista and sagecell with a wrench script that lets you run a script edited in pythonista on a sagecell server)