Cheap Garmin recommendation for Segment Hunter

Happy Karoo user, but Segment Hunter looks cool and I want to try it out, so I’m thinking to buy a cheap garmin to play around with it. Can anyone recommend a model? Edge 520 seems cheap second hand.

I have a 520 and have been mostly happy with it, but I get constant disconnects / reconnects with the phone. I don’t know if this is common to that model or if I got a lemon. Otherwise I like the 520. Not a lot of memory if you are loading other maps (e.g. from OpenStreetMap). I ran out once and had to delete stuff (old activities). I’m thinking an upgrade is in my future though when the next generation of 800 series comes out. Or I’m thinking maybe just using my phone as a cyclometer (not sure how that will workout on the mountain bike).