Often, a small local mill shop will have something that will suit your situation. Someone who does hardwood flooring may be able to help. They would build it up from different cutters or might have the one you need for your baseboards.
Usually they charge a set up fee, a deposit in case of metal in your lumber (nicking their cutters) and then a surprisingly small amount of $$$ per foot of milling.
Your boards could have been done using multiple hand planes, which is another option you could go if you don't have a huge amount to do. Using a combination of hand and machine tools.
Also think about 'stacking' seperate pieces. It'll make it easier to mill each piece, then build it up to where you want it.
It would be helpful if you could draw or trace a piece, then I'm sure someone here can come up with an idea to fix you up.
Welcome to the forum!