I like your idea of a bag with mug rug, mug, and goodies. Mug rugs are pretty easy and cheap to make with scraps (I made 14 in an afternoon last year for our library staff - took me an afternoon). But the mugs will be expensive, no?
What about sets of coasters made of 5 charm squares and a piece of batting? Tie them together with a nice ribbon or piece of scrap fabric.