As Doug says. It isn't hard to make your own lug or BB. 4130 tubing is easily available from a number of sources and in a considerable range of diameters and wall thicknesses. BB shells that are straight/threaded "tubes" are also widely available. Most of the self made lugs that I see are brass brazed together. If the shore lines are ornate they are created after brazing the blank up.

A couple of questions though- What material will the fittings (Bb shell) need to be? Steel? This effects what filler/joining you use. Are these fittings going to be external to the bamboo? Or do the tube "stubs" fit up inside the bamboo? Are you up to speed with the different types of bamboo (for frame making) and your growing climate? I have a thread on a recent lug and BB making project here: Lug Making Andy