Heads up, the Orbweaver is an update to the Nostromo, which doesn't rate wonderfully on Amazon.
The Orbweaver is a pretty good little thing though, as well as the Logitech gamepad.
o-rings? really? They are cheap and come in packs of hundreds. I have some 5/16 inch NBR (nitrile) ones that work really well. just pick what hardness you want, or get some of each to try.