Etrex 20 is great for navigation. Bulkier and a little bit more of a faff saving rides than the bike specific ones, but robust. Popular with Audaxers, partly because it takes AA batteries which can be replaced mid ride. And you’ll get 25 hours out of a set of good batteries…
Get a lanyard to be on the safe side and attach it to your bike. It’s not entirely uncommon for them to slip out of the mount (I’ve lost one myself).
Edit:
If you do get one, be aware that they only take so many route points. If the route you save has more, it’ll cut it short… I found this the hard way. You can save as route or track. Easier to save as track to be on the safe side. But I always check the full route is there before leaving the house now!