Here is the list of 3 ingredients (you are likely to have at least 2 of them in your stuff right now):
1. Tingley Natural Rubber Work Overshoe, 17" kneeboot. Local Farm and Fleet, Tractor Supply, etc. likely have them.
2. Felt Pak Boot liners, you know like in the LaCrosse brand of pak boots that save your toes on the deer stand. (Take this to the store, put one on and try the Rubber overshoe on for size -- the boot liner IS your inner boot.)
3. Removable inner sole from your work boots (Red Head makes a good one for arch support). Put this inside the overboot, below the felt pak.
Cheap, warm (take an extra set of Felt Pak boot liners for a dry replacement, enough room for one or two pairs of heavy socks), flexible, waterproof, comfortable, and did I say cheap?
I know, along with your paddling garb purchased from the Goodwill store vs. Bean and Co., you're gonna look like the creek bum hick wanna be that disqualifies you from the club, so get on with the poor boomer, subversively tight, retirement plan (yeah, I know, showing up looking like a bum paddling your black gold luxury boat ain't exactly congruously, harmoniously consistent, but keeps em all wondering about your rightness all the same).