At one time, it was a common practice for some trout anglers to add a small spinner & clevise to the tippet ahead of a fly, even with fly gear. I used to do this frequently enough when I was a youngster, and caught many panfish as a result. Didn't do it much for trout, as trout fishing came along for me later in my life and I stuck to flies. It can be a very productive technique however. If you decide to go that route with a fly rod, use a small folded clevise & size 0 or 00 Colorado blade ahead of the fly. This works well with wet flies (size 10 works well) & streamer patterns, and a bead or two should be added between the clevise & knot. You may need to go a bit heavier with the tippet than you might with flies only, as a spinner can twist a tippet & leader unfortunately. It's been discussed on this forum how a tiny swivel may be useful with flies, so the same would certainly hold true with an added spinner blade.
Otherwise, the smaller size Roostertail spinners tossed with ultralight spinning tackle can be great for targeting trout, and/or panfish. I like throwing the smallest size jerkbait or crankbait lures too on ultralight gear. Even small stream SM bass can be loads of fun on such a light outfit & lures.
I still use other gear besides my fly gear, and generally remove trebles on lures & replace them with debarbed single hooks. This is better for the fish, makes releasing them easier & lessens the chances of a nasty flesh wound with the trebles.
Here's an alternative too. This one is a bit larger, size 4 hook, and something I'll only usually use for panfishing, but could be productive targeting trout.
