Global Market only Shows Donuts, Batteries, Detonators, and Watches

I need to expand but if the items I need are never on sale how am I supposed to do this.  All I can see in Trade HQ is doughnuts and batteries. The dozer blades and exhausts appear very occasionally but only when my storage is full so I can't buy them anyway. Is this a flaw or programmed like that on purpose. Trade HQ is pointless.  Very annoying how long it takes to get to a sale item which then disappears before you can buy it. Should be able to select more than one item at each visit.