Welll. . .I’m sorry this is not the perfect answer, but here’re some ideas.
If you look on rav for “pullover” “raglan” “placket”, there is a child’s pullover which is sort of like what you’re wanting. BUT it comes from a book called The Complete Book of Raglan Sweaters by Leisure Arts, and that sweater (“Placket Neck Pullover”, no. 7) is designed for from 6 mos. baby to size 50 adult! As is “Basic Seamless Pullover”, no. 8. So here’s what you could do–
Instead of the ribbing at the bottom and cuffs, just do seed st. At the neck, if you like the placket, then just follow their instructions for no. 7. But if not, then do no. 8, and a few inches before the neckshaping begins, split the front and work the right and left half at the same time. At the split, do seed st for a few sts on each side. Then just follow the neck shaping as instructed, but keeping the split. For the neck band, instead of ribbing, do seed st.
Hope this makes sense, but I think it won’t be too difficult to adjust this pattern. Unless you get really lucky and someone else here recognizes it and can send you to the exact match!