Cheapest way to get CEUs?

I used to work for a tree company that would submit my weekly tailgates for CEUs. But now I’ve moved to a utility where I don’t get that luxury. I have 3 certifications, and need 39 more CEUs. I know isa offers quizzes but they’re very expensive for very few credits. They’re charging at least 10 dollars per 1 CEU, which would amount to 390 dollars minimum to get the rest of my CEUs. What has been everyone else’s solution outside of using your company issued exercises submitted to ISA?