I'm sorry that your first experience with Mamapedia involved one or more responses that upset you. We have a diverse membership and not everyone expresses things well. If your question was very brief (and I can't tell what you originally posted but it's obvious that you added some info), some may have assumed you were not serious. That's a big jump, I know - but we have had a bunch of one-line questions lately that are from trolls, so a few people may have jumped to the wrong conclusion.
Adding details would help, as you can see from the kind and generous responses. Where he is on the autism spectrum makes a difference. But all kids with autism aren't the same. Some can't stand to have tags inside their shirts and can't stand how their socks feel, others have zero social skills, others can't stand noise. Some can speak, others cannot.
Is your boyfriend an active father who is in touch with his kid? (I ask because if he's been prevented from seeing much of his child, it can be hard to know all the nuances.) Or is this all new to him too? If he can help guide you, that's great. You could also look into a support group for parents and caregivers of kids with autism.
Is the child getting any early intervention services through the school system? Has he been seen by professionals who are helping to get him ready for eventual kindergarten? Is he in preschool? The teachers may be able to help you with ideas.
If this boy doesn't like people or zoos, it may be the noise or the commotion that bothers him. If he likes the outdoors, you could try some nature areas with few people around. Maybe get one of those ant farms or check out toys for kids who love bugs. Maybe a quiet half-day of kayaking or fishing would appeal to him.
If he can focus pretty well, don't underestimate the value of building sets - Legos, K'nex, etc. If noises bother him, get things that connect well rather than things that stack and fall over. If noises don't bother him, consider one of those marble sets where you stack and connect the tubes and slides, then drop marbles in the top and watch them cascade down in different patterns and routes. Having a supply at your house or your boyfriend's may make the child's transition easier if he is leaving his mother's house and going to his father's - sometimes change is hard.
I see the suggestion below about a big box for a fort or clubhouse - some autistic kids like to be enclosed and shut away from activity, so that might be a fun option. See if anyone in the neighborhood is getting a new dishwasher or fridge, and ask if you can have the box. You might check with a local appliance store to see if they are delivering something new to someone, and ask permission to take the box when they are done.
Do learn more about his particular type of autism and how it manifests. A good children's counselor experienced in this area might be a great resource - ask the pediatrician for a referral to someone who accepts your boyfriend's insurance, and see what you all can learn that is specific to this child.
Good luck - it's an ongoing process. All kids change as they grow and mature, and kids with autism can offer a special challenge.