Well, since I can't tell if this pattern is still copyrighted, here is my feeble attempt at a tutorial.
You will need to adjust measurements based on your wee one. My daughter's chest is 21" (about a 3 or 4 T) so my measurements are based on this, and include room for ease and seams. PLEASE REMEMBER THAT IF YOUR CHILD IS LARGER OR SMALLER, THE ARMHOLE WILL NEED TO BE MODIFIED ACCORDINGLY. I didn't take this into account when I first made the tute. The width of that area just above "A" in my pattern was 4" (across DD's side from back strap to front bib) which corresponds to DD's actual measurements around her side.
There is only one pattern piece, and this is what it looks like:
Please ignore the inside of the two lines on the left- it is nothing but I was unable to erase it for some reason.
Here are some numbers to help you develop your own pattern:
The total measurement across the front was about 25 inches. This is my daughter's measurement + 3" for ease. If your child is much bigger or much smaller, the ease measurement will change accordingly.
A to B on mine is about 6.5"
C to D is about 18", which includes 5/8" seam allowances
E to F is about 26" (incl. seam)
G is 4" above and 1.75 inches to the right of A
H to I is about 17"
I'm not math-minded enough to figure out the ratios for you, but if you fiddle with that enough, I'm sure you can come up with your own pattern quite easily.
Now, fold your material (following the grain) and place the straight edge of you pattern (C to D) precisely on the fold. Trace and cut.
Do the same with the lining or contrasting material.
Pin the two fabrics, right sides together.
Sew together, leaving an opening to turn.
Turn and neaten edges. Sew opening closed.
The buttons you choose must be of a similar size, or you can use another method like snaps or whatever.
Attach buttons to front and back of jumper top (if reversible.)
Small one modeling.
Sorry if that is terribly unclear. I'm not a good computer artist nor necessarily good at explaining things. Any questions, just ask.
I'd love to see your version!!!