The term itself
A head spa is scalp work sold as the appointment, not as a step inside something else.
Search head spa Wichita KS and you mostly get video — warm water, slow hands, somebody with their eyes shut. Underneath the styling it's a narrow idea, and an easy one to say out loud. A head spa is a session where your scalp, the back of your head and usually your neck and shoulders are the entire point, not the bit somebody gets to on the way to a haircut. Your hair gets washed because scalp work is wet work. The hair isn't why you're there.
Everything after that sentence varies enormously. Sessions sold under this name run short and long, some worked seated and some reclined; one place means a scalp massage with water attached, and the next means an hour of quiet under a warm towel. So don't assume the version you watched online is the version you'd get anywhere near here. Ask what this one is, and the answer comes back in a sentence.
Crystal Massage offers a head spa. The studio's own brand mark carries it — the name, and under the name the words Head Spa — and the owner confirmed the service is on. What the owner didn't supply was a length or a price, and nothing here invents either. So the service exists, the figure you'd pay for it is one phone call away, and what's left is working out whether the thing itself is what you actually want.