MacRumors takes a look at the Chipolo ONE Spot
A quote from the article:
The Chipolo ONE Spot is the first Find My-compatible accessory that's a direct AirTag competitor, offering AirTag-like tracking capabilities for your valuable items. The ONE Spot is slightly more affordable than the AirTag at 28 for one and 90 for four (vs 29 for one AirTag and 99 for four) and it has a couple benefits that make it a worthy AirTag alternative.Chipolo ONE Spot Review
Like the AirTag, the ONE Spot is a small, circular tag that's about 1.5 inches in diameter, so similar in size to a silver dollar. It's bigger than an AirTag, and about as thick, but it's a uniform thickness, whereas the AirTag has a protruding bottom where the battery is housed.