Ok anybody know where i can get either a stock 6x8 stock speaker or anything else that will fit and sound good?

a 6x9 is too big for the space given not even sure how speaker is held in place?
it looks to me that speaker is or was held by a pair of S clips that slipped over the mounting studs then tightened down.
got radio hooked up to a small cruddy 4 inch speaker

for testing to ensure it worked properly so now i need a more permanent solution. I guess maybe hit Goodwill or other thrift stores or some rat hole audio place maybe the corner mexican stereo shop see what i can come up with as i am not looking to buy a new set for just one speaker.
any help is greatly appreciated!
Thanx
larry