you can buy twinax cable -> Amphenol E321471 Aipc 571540012 SFP 10GbE SFP Twinax Cable 1 Meter | eBayI just ordered 2 Chelsio NICs that came with 2 TwinAx cables. Knew nothing about them until I read this thread. Thanks.
start best offer with $4 each and maximum $5 each
the seller is very responsive, even you submit low-baller price . this is the same seller that you bought i340 .
the shipping is depend on your location,
I bought 3 total with shipping is ~$24
two melanox X2 $30 + 3 twinax cables $24 , I bough extra cable for planning to buy more X2 in the future when the price is down further. very affordable to get 10G upgrade. Still looking for the switch.