I would agree that there are better solutions , because as mentioned in the links, the field coil functions as a choke, wheras a resistor won’t. that said I have successfully gotten radios to work using a resistor, I have even seen where a previous owner had replaced the speaker with a more modern permanent magnet speaker,but retained the field coil so it works as a dropping resistor as well as a choke again a repair but perhaps a Kluge.
Now you didn’t mention the size of the speaker. Keep in mind that there are a lot of radio/phono combo radios that were somewhat boring and may have been gutted so larger speakers ( say 10 inch) are a little more abundant. The speakers for cathedrals and tombstones are often a bit smaller and since those radios are a bit more desirable to many collectors it seems that smaller ( say 5 inch) speakers are a bit harder to find. If you find a donor you will like to find one that is close to the same as far as the resistance of the field coil goes. It mayor may not be on the schematic.
Depending how many parts sets you have at your disposal, the best fix may be just to look for a donor radio, or if you want it perfect you may seek out the services of a speaker repair business that will work on older field coil speakers.
Older radios such as ones from the 20’s may have a high resistance fild winding in the neighborhood of 2000 ohms and you may find it a bit more difficult to find replacements, but many of these type of radios had separate speakers.I am kind of making the assumption that your radio is one from the 30’s or 40’s just because they are a bit more common. Dont take any of this as gospel. I have limited electronic bench work experience but thought I might add a tiny bot of insight and perhaps some ideas.