I think I mentioned this on a thread about corsets in another group
ages ago, but for boning I've been using 1/4" polyethelene tubing.
You can buy it at hardware stores. Around here they use it to hook
water to evaporative coolers. It's really cheap stuff. If you cut
it straight across and don't fit it in channels too snugly, you won't
have a problem with it pushing through. It's flexible and machine
washable. It has a slight curve to it, but I've used it on straight
elizabethan corsets successfully. I can say its a bit more bulky
than rigilene boning. I have also used it to hold out panniers and
hoops. As far as I know it comes in 4 colors, I have copper
colored. Recently I made a pink "diamonds are a girls best friend"
Marilyn Monroe and boned the inner bodice shell with it, worked great!