It needs to support Firefox, Safari, and IE, thus it must be able to draw using VML and Canvas accordingly.
I've attached a script which is much more complex than what I'm after, so the intended functionalities make up only a small subset of it (along with some adjustments). You can base your code on it (it draws using VML and Canvas too).
This should be a simple script, so the budget is well below $150. However, it needs to be well-documented.