What are you looking for? Ready to go?
Stripped?
Optic cut?
Plain?
There's tons of options.
PSA Dagger slides are useable if you don't care about the finish wearing down. My experience with their ceracoke is complete garbage.
If you want an RMR cut, theirs are shallower than others. But useable.
I'd definitely replace the striker with OEM Glock if you're using it for anything serious (defense, competition, etc).
Sights are reported to be very hard to remove (but if you like them, they probably won't fall off).
Remsport makes a nice Gen3 slide with Gen5 looks (if you like that). Better finish than PSA or Glock in my opinion.
Grit Grips is selling slides stripped, plus complete parts kits. I'd buy one of these frames before a Dagger frame (and I own three Dagger frames).
https://shop.gritgrips.com/stripped-slides/Stay away from combat Armory slides. Might be cheap, but also complete garbage.
Brownells had great deals on their usually overpriced slides. I'd opt for the hole in the top to not have the goofy looking serrations that wrap around the top of the slide.
If I were an operator, operating operationally, I wouldn't be using a home assembled handgun