I make a lot of machines and robots for a university laboratory, and I agree with the others, the cheapest custom parts get isn't cheap. First look for something very close that requires little or no modification, a sight like mcmaster.com is a good place to look. If you can't find that go to a machine shop and give them very good clear plans, be sure not to add any features that will add work time but not value. You would be surprised how often people put some complicated round or fillet on something that could just be left square.
For example for what you are trying to do I would look for parts that can do what you want pre-made, knowing the proper names to find parts is key. Maybe you could just get a shaft support like **broken link removed** (probably not the size you need and you just need one) and drill holes in a plate and mount it on there.