You can buy water based stains at hardware stores and such. Bear (Beere, Beare?) is a pretty common name. However, I will caution that I've had bad results with these stains, particularly Bear. They dried very quickly, like latex paint, right on the surface. I had a difficult time getting penetration prior to drying, and then had to wash the scum off the surface of the wood.

Mark came up with the novel idea of using laundry dies. Readily available at grocery stores and such. He reported good results as far as color went, but very shallow penetration. Can't remember if he was soaking the wood in a solution, or brushing it on.

Myself, I'd be very inclined to try the laundry dies. The color range is fascinating, and I suspect one would have the least problem with epoxy adhesion using these dies.

They also won't make you sick if you ever have to eat your kayak as a survival food.