[K5EAG]

If you can't find the correct 8-inch field coil speaker, it is possible to replace it with a common 8-inch permanent magnet speaker.  You still need an output transformer, but you can buy a suitable one from someplace like Edcor, https://edcorusa.com, or AES, https://www.tubesandmore.com.

However, you would have to substitute something suitable in place of the field coil in the power supply circuit.  Often a power resistor is used.  A choke is a better substitute, if you can find one that's similar to the field coil of the speaker.  Look at Edcor and also at Play Things of Past, http://www.oldradioparts.com.

Thanks so much for your reply and suggestion.  I may just try your suggestions.  Thanks again!