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
https://forum.omz-software.com/topic/5014/shape-method-for-turtle-py
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)