New speaker for old radio?

I took apart my stock mopar radio today. (The manual says it's a model 203 but on the bottom of the case it was marked 103.) I used tuner cleaner and now the radio is like new. However, the 47yr old speaker is tired and I would like to replace it without going crazy. I traced the size on a piece of paper and measured it a 6in.x9in. What kind of speaker would I use to replace the original? The speakers on sale all appear to have modern applications, and have a zillion watt-capacities...AND...they all come in pairs!

Any suggestions?

P.S. I forgot to measure the thickness of the original, but anything thicker probably will not fit.

-Dan