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It's possible to build an FM broadcast band downconverter to get FM stations from part of the 100MHz modern FM band converted to the 42 to 50Mhz range this set will tune. The FM preemphasis and deviation of the modern 100MHz band is very similar if not the same that was used back in the prewar 45Mhz FM days.
I said "possible" as building VHF circuits is not easy. Maybe the easiest approach would be to take an existing working but junk FM radio and change its LO from being 10.7MHz higher than the desired FM frequency to 45Mhz higher. Or 45Mhz lower (though you'll get "birdies" in the reception, like the 2nd harmonic of the LO).
Maybe better would be to use an old TV set tuner. Set it to channel 6, and futz with its LO to push it up into the modern FM band. Connect the Stromberg FM antenna to the tuner's IF output cable. Note that TV station sound FM uses less deviation than FM radio stations, and will have lower volume. Before you adjust the LO try tuning in an existing local TV station and tune the Stromberg FM set to around 41 to 42 MHz. You should be able to pick up the TV sound signal. Also play with the TV tuner's fine tuning.
Of course you'll be wondering if the Stromberg's FM is even working. If you hear "FM" hiss, that would indicate that at least the IF strip works. But what of its LO? try playing with an old baby monitor (the ones on 49.86 or such frequency) or those toy walkie talkies from China (those are AM, but will produce a receivable blank signal, or tune off slightly and you should get distorted audio when the user talks or presses the "code" key).
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