You can do it with your Minera too, you need to use this cgminer fork https://github.com//usb-miner/tree/master/software/cgminer

Build it in your Minera system, then copy the binary "cgminer" to /var/www/minera/minera-bin/custom directory (with a different name like cgminer-gridseed), go to the settings page and enable it under "Custom miner".

Finally you have to setup it with this option: --gridseed-options=baud=115200,freq=800,chips=5,modules=1,usefifo=0,btc=16

Or follow this post, section 5A.2 https://bitcointalk.org/index.php?topic=494625.msg5448813#msg5448813

EDIT: Here is the binary built for Minera: https://mega.co.nz/#!ucEGkBJC!3fdUPgjrubnF59-CUvVKw2aNTWTxu9Rg6jWxXJduEpM

where the best site to buy gridseed in europe.
thanks in advance