I can't say whether the contacts are specifically for J-Cell, but AVX and ITT-Cannon have excellent lines of spring contacts designed for the mobile market (hand held in particular).
I use a dual row stacker that might be suitable
58-9158-030-000-037S from Elco (part of AVX).
As always, check the stuff for your own application.
I prefer AVX/Elco as the support seems to be much better than ITT-Cannon (it's almost impossible to get them to answer calls - one wonders if they actually want to sell anything).
Cheers
PeteS