i'd highly recommend making the investment in good boots since over time you're down to pennies per use and while it's impossible to calculate how many injuries they'll prevent, there's a good chance an upfront investment will save you money there as well...
but if you don't want to do that... what i do on trips where i'm flying somewhere, traveling light and size 13/14 wading boots are too much.. hit a discount store like payless, marshalls, ross, goodwill, consignment shop, whatever, and pick up a pair of cheapo boots/shoes a size too big. most recent time i did this was out in central washington this past fall and picked up a pair barely used of designer boots that should have been $150 for $8, the old lady running the store almost didn't sell them when i told her i just needed something to wade in for a few days. they work, but the rubber quickly hardens/degrades and certainly a lot less traction and support than good boots.