[TSOJOURNER]

I just made some from white oak. I sailed with them last weekend and they seem to be fine. I just pretty much made them fit the pockets; roughly yardstick shaped. Sanded smooth, no finish. White oak puts up with some wetting/drying well. I would not use red oak. I would have considered ash as an alternative.

 

[TSOJOURNER]

On a larger boat, fiberglass battens may make more sense, since the weight and stiffness of hardwood battens, compared to extruded fiberglass ones, may not be as appropriate. Many sailmakers will have batten stock for sale.

This is his boat:

 

[TSOJOURNER]

Best batten material I have found is the "unbreakable" yardsticks. Wood yardsticks work too, but the unbreakable ones will not warp or absorb water. I have equipped more than one charter boats with missing battens this way But when the sail gets wet you can see the numbers...