Ru is about 6.5 pounds and nearly hairless. I just checked, and basically anything he wears on a regular basis is 3/8" or smaller. He is also walked on a harness, and a paracord leash (not braided, literally just a single cord) which basically makes him look like a rat on a string.
Cheap collars are cool, as long as they actually come in super-tiny. I was looking at Spindrift but they seem so bulky. I like Up Country collars but most of their patterns don't seem to transfer down to miniscule size.
Dogs by the Bay has some really cute stuff! That awesome shark collar only comes in 1" and wider though, and Ru is only about 1" from his ear to his shoulder. A lot of fabrics don't look as good in teensy strips.