[Texasrocker]

Hello M100C. A good way to sub for your open Spkr field-coil is by using a modern-type wirewound power resistor. According to Rons orig Philco Spkr data here, your orig spkr ( mod K-3) had a FC resistance of approx 3100 ohms.
Until you can find a orig replacement, or have your vintage spkr repaired, you could sub a 5 or 10 watt power resistor of approx 3K- to 3100 ohms as close as possible to 3100 ohms. You can trace back to your chassis orig spkr connection ,the correct 2-pins that originally used the spkr field, disconnect those 2 wires, then solder in the new ceramic wire-wound power-resistor across those 2 pins under chassis on the orig female-side of spkr connector. Since the orig spkr voice-coil was 0.7 ohms, using a modern pm type 8 ohm should work fine. Monitor the heat of the new power resistor if you decide to use one, as it will get hot which is normal in this case. The 5-watters usually are all I use, however the 10-watters will operate with less heat dissapated, but take up more space under the chassis.Hopefully, you can find a good orig spkr in the future if total "originality" is your preference. I have found the modern pm type full range spkrs usually sound much better overall anyways compared to the originals.Just my opinion though. Good luck with your vintage Philco restoration!