The Tack Trunk at 11517 E. Trent, Spokane, WA 99206 (509) 927-5891 always had everything I needed, or she was willing to get it if not. I moved away several years ago, but a quick search shows she's still there running the shop. You can see it online as well at www. spokanetacktrunk dot com (leave out all spaces)
There is also Foxy Horse and Hound at Latah Creek Plaza, 4241 S. Cheney Spokane Rd, Suite "B", Spokane, WA 99224 (509) 455-3609 and also have a website at www. foxyhorseandhound dot com (again leaving out all spaces)
I don't know the 2nd shop, not sure it was even there when I lived there, but the Tack Trunk I do know. I went in all the time and Viv is a lovely person, easy to deal with and honest.
Have a good trip! ps. I am so jealous you get to go as I am quite homesick!
"Life's a bleach and then you dye"
"Some people walk in the rain, others just get wet." Roger Miller
It is probably worth noting that Foxy Horse & Hound is not open on Saturdays but is open on Sundays. If you end up there near a mealtime - Chaps across the parking lot does great breakfast and lunch - Latah Bistro has yummy food too (lunch/dinner).
Also, not sure if Cheney Feed has much left in inventory but they did have a lot of stuff on consignment from a tack store that closed - prices were marked way down.
I didn't see this thread in time, and I see that no one mentioned Indiana Harness, which used to be over by the racetrack, convenient for the backstretch people and other riders alike (at least I think it was). I haven't been there since the 80's, but it used to be a lot of fun to visit. I don't know what I'd think about it now, but if we were there in the area and had time, we'd sure stop by. It still has a Yellow Pages listing, so I think it might still be in business.