If you want small/robust and pretty cheap (and I'm no fan of using phones for this - folk finding that their FB twiddling has screwed their GPS battery as the wolves circle) I can recommend the Garmin Etrex 20. Or the 20x, which has more memory and apparently a higher resolution screen, though some will advise (I don't know) that the latter feature makes the screen, counter-intuitively for a non techie like me, less readable.
Etrex 20 now superseded but will still be available used via
ebay. I have one - any questions fire away.
Very tough. Highly waterproof. Runs off two AAs which can be rechargeable so you can carry and pop in spares as needed - only the most foolish with a death wish will run out of power. The extra memory of the 20x isn't strictly necessary. The memory stores waypoints essentially. Has a card for putting maps on. I use maps for free from
http://www.openfietsmap.nl/
essentially these are Open Street maps flavourised. check out the website to see how the global community-generated maps are in your patch. Even if the maps are poor in your area or you manage to screw the installed maps, you can of course get the unit to straight line point to a chosen point on planet earth or to a waypoint you had previously put in. You can of course get it to plot your outward ride and then just follow your line back.
If it helps convince you, for years I laughed at the things but am now a convert. No need to spend more than the 20 or 20x, in fact some of the more expensive Garmins are in my view less fit for purpose. Quite rare to see the Garmin Etrex 20/x in a UK bike shop as they would prefer to sell you something more expensive. A very good compact handlebar mount is available from Garmin though I advise also looping a small light lanyard through the bar. Recently rode 140 miles through the night in the UK with mine or a route I had previously put in - faultless and still battery power left at the end.