Good under-seat bag for Strida?
Once again looking to harness the power of collective knowledge ...
I would like to have an under-saddle bag for my Strida - the kind that attaches to seat rails (and often, the post).
There is a custom Strida option, but a) it's $50 - high compared to the cost of non-custom options and b) at Areaware at least, not in stock until December.
It does seem to me that most seatbags with a seatpost strap (usually velcro) won't work that well, since the Strida seatpost is made unusually thick by the plastic clamp apparatus.
Hence my question to other Strida owners / seatbag owners - what seatbags do you know / think would work well for a Strida?
Haven't researched much myself yet other than REI. They have a small Novarra bag that could work - no seatpost attachment - but it looks like a fairly small bag.