doesn't look like the U, M & P's are the same between stump and jumper so I'd guess it was a hand-drawn logotype.
Why not just sign your name with a thick marker, then enlarge it on a photocopier and trace it on the computer. If you add a drop-shadow in black like the stump jumper logo it'll look fantastic.
I've been meaning to get some stickers like this done for my own bikes to personalise them.