These bamboo placemats come from Amazon. The reeds are approx 1/16 x 3/32 and are oval shaped. The 1/16 side bends easier than the 3/32, soaking or heat should work. I'm going to try these out for wingtips. There are enough reeds to last forever!!

https://www.amazon.com/gp/product/B0021Y69HG/ref=ppx_yo_dt_b_asin_image_o00_s00?...

Nice find and I'm sure they could be stripped to make stringers, but I'm afraid they would be much heavier than the balsa stringer of similar size.  You could weigh them to compare.

Bamboo is very hard. You can 'split' it with a heavy craft razor blade, or an Xacto knife, but it does not split 'square' because it doesn't have the same kind of 'grain' as our usual modelling wood does. Bamboo skewers are cheap, try some and you will see what I mean. You will have to split roughly to size and then sand to shape. But you will have to change the sandpaper out often because bamboo is very hard on sandpaper. It might be easier to split flat stock, which is why I mentioned the bamboo coffee stirrers. They are only 5 1/2 inches long, but that might be enough for wing tips.
ian

Alfakilo... here's the link Mike referred to: Click Here

For bamboo I use skewers in the bulk packages for shish-ke-babs at the super market.  They split off easily for strips to be molded.  Another source is bamboo placemats that you can rob the bamboo from...just don't take the wife's placemats...not good to do this!!!! Don't ask how I know!

  You could try fly-fishing shops since good bamboo is used in cane rods. Or you could pick up some bamboo coffee stirrers from the dollar store and strip and sand to shape.
ian