We are all Yorkie Crazy here !
I'm sure there must be a website that has free instructions for knitting and crocheting sweaters. Last year I knitted 3 sweaters for my daughters Italian Greyhound of which their body shape doesn't even come close to a yorkie.
I'll see if I can find some knitting and crocheting patterns online for sweaters and will forward them here.
Great Job 'waistfull' by the way on creating the sweaters, keep up the talent!