Even though he's not Polish, I think Uli makes the best kielbasa in the area. Some local groceries carry his sausages, but I don't think I've ever seen kielbasa - you may have to go to his stand at the Pike Place Market.
Kruschiki will be tougher if you're not going to make your own. You might try Cafe Yamarka and/or Piroshky Piroshky in the market while getting your kielbasa.
Alternatively, visit or call up George's Deli (9th & Madison) - they don't have pastries IIRC but they may be able to steer you to the right place.