For reference purposes: Vintage Tamagotchis have ⌀ 2.4 mm bead chains.
The one on my P1 measures ca. 12.3 cm (including the connector) and has 36 beads (including the ones needed to connect the ends). Bead count may vary (see this topic: http://www.tamatalk....in#entry3195779 ).
Hope this will help anybody trying to buy replacement bead chains. Knowing the correct diameter sure would have saved me some time and money.