walk the local thrift shops
Check your local Craigslist /Ebay/gumtree
ask your Friends to donate
Just what i was thinking, as pretty much else is your local store and were all know what they are like.
We found some a few months ago, a pair of HyperX branded ones at Goodwill for $7. i checked them over for my daughter and made a deal with her that she pays for them i will fix them if the cables end up being bad. but they were perfect working order. good Quality as well.
some times you can find the logitech mics cheap on ebay some times.