Electronics Repair Questions? Ask an Electronics Technician
Hello and than you for the question. Yes, what you're looking for is known as an "AM Loop Antenna" and they are somewhat rare to purchase, as most are included with new receiver purchases- but not generally for purchase otherwise.
However, there is a company that produces a premium AM loop antenna (Terk) which would allow the HK receiver to pull in at least as many (likely more) stations than the Sony clock radio.
This antenna is around $36 and can e purchased at the link below. It also connects to the AM antenna terminal on your HK receiver via the single wire hookup:
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