To the best of my knowledge, there are no manufacturers that do not use the ‘plastic’ coating on their spline stubs and they have not done so for decades. Truthfully, tests have shown that if the slip yoke & spline stub is well lubricated, the ‘plastic’ coated splines last much longer than bare steel. Ultimately though, I don’t really think the manufacturing decision was based on much more than cost, as the bare steel splines were very expensive to make.
It is for liability considerations that we do not sell any weld in components other than to qualified drive line shops. Our products liability insurance does not allow us to do so.
Assuming everything else in your drive shaft is in good working order and allowing for; the slip yoke, the spline stub, 1 universal joint, in the slip yoke, rebalancing the drive shaft and returning to you (UPS Ground, lower 48 states), the total charge for the work you request would be $185.00.