Once you know how much money you'll need, where do you find it?
Request a grant from the Python Software Foundation
Start here. The PSF has a very generous Grants Program designed to support Python-related events and activities, including educational programs!
A complete, detailed description of the process can be found on Python.org's PSF Grants page.
From the FAQ:
So, for a class of 30 students, you could request up to $1500.
A PSF grant will cover the majority of your classroom expenses, but if your budget calls for a little more:
Reach out to technology companies that use Python
If you're a Python developer yourself, start with your own employer.
After that, move on to other companies involved in the Python community. Look to Python event web sites to find out who sponsors them. Check with your local Python user group to see who can contact their own employers.
When you contact these companies, always be polite and professional. A quick Google search will turn up a number of email templates you can use to format your request:
Contact local companies and civic organizations
It's a good idea to cultivate local sponsor relationships - you never know, you may have so much fun that you find yourself wanting to teach this class again and again!
Even local companies that don't work directly with technology have a vested interest in improving computer science education in their communities.
Try children's museums and universities - the same places you might be looking to for venues.
And don't count out local restaurants and small retail businesses - a few hundred dollars is a small price for good publicity for them, and will go a long way for your students.
Other education grants
Did you know that the U.S. Department of Education administers a Eligibility page to find out if there are funds available to help support your class.
Setting up a PayPal account provides an easy way for sponsors to send money, but be aware that there will be service fees subtracted.