If you are going to seek fulfilment for parts of you outside of your marriage, it is important to have your wife's consent first. It may be a very difficult series of conversations, but being open and honest with her truly is the best way. I know its easy to get swept up in all this, it all comes from the core of our beings, but fall for it and step away for a moment before you decide to dive off a cliff into the water, so to speak.
As far as finding Mommies out there, that's a lot harder to do, and I honestly would not know where to point you.
I'm going to assume, against my better judgment, that your wife knows about your interests and just isn't into it. So, at the very least, you need to discuss with her your desire for part time anything. There are plenty of pay services out there.
First, talk with your wife about your needs. Please respect her!
After you talked with your wife, let's talk about your options. First, finding a mommy is very hard because the math does not work out. The proportion of females in the community is about 1/3 based on my observations at conventions. The proportion of females who want to be mommies is also small. If we assume every mommy is exclusive to 1 person, then the mommies have their pick of the crop. It is very likely as a male abdl, one will never find a mommy.
Your second option is to engage with the community and make friends. It is way easier to make ABDL friends! ABDL friends are willing to baby you and it is very realistic. Everyone can have multiple friends and friends are not exclusive to each other so the math works out.
Your third option is to purchase mommy services. This is realistic because there are mommies who sell their services.
Option 2 is realistic and fulfilling. Option 1 is unrealistic and fulfilling. Option 3 is imo expensive and I think probably doesn't satisfy the urge like 1 and 2.