What you purchased is generally called a "book of business" or "customer list" and falls squarely into one or the other or both of these items listed as intangibles:
"Business books and records, operating systems, or any other information base, including lists or other information concerning current or prospective customers."
"A customer-based intangible."
The amount does sound rather small and I'd guess you'd probably get away with expensing it as something or another, (you might even expense it on line 27a as "Customer list" - providing "full disclosure"), but technically, yeah it probably is an "intangible."
