[Texasrocker]

Hello Radiorich,
Bet you can find a replacement antenna to fit your needs at a local garage/sale or secondhand store than has a old busted plastic radio case from the 60s tube radio era.
Just about any good used loop from any type radio will work. Many times, old radios in bad shape cosmetically yield some good spare parts, and dont cost very much at all. I usually offer about $5 tops for parts type sets, and have purchased many for less over the yrs.
After looking at my Riders schematic, the orig missing antenna loop for your set was 3.6 ohms total. The outside loop connection of the antenna connects to the tuning condenser section that feeds grid of the 12BE6. The inside of the orig loop terminated to chassis gnd via a 5 mmf mica type cap in series with a 150k 1/4 watt resistor, and/or, could be used ( lifted) from chassis to connect a outdoor longwire antenna to the inside loop for long-distance reception.
Just bet a flea market cheap-set will yield you a good antenna you can retrofit. Take along a small ohmmeter and you can check any old used loop antenna you may find in a parts set to matchup to your needs, by adding or subtracting a few turns of antenna wire. Best of luck getting your vintage Philco restored!