I follow the fab Max and Paddy in the lakes on Facebook, and they use the Ruffwear collars and harness.  I asked what size they recommended for a puppy and they told me the xxs.

I found it to be cheapest from Amazon 

We had decided to stat using a harness straight away any time Dakota goes out, then she will just see it as normal to be wearing it. And as Max and Paddy’s owner pointed out, they are also great for grabbing onto a wriggly puppy!

Dakota has been happy to wear hers about the house for a bit and then when we have gone out in the car and for walks (carrying her)  It feels so much more secure than a collar.  And is easy to put on with 2 clips on the side.

This version has a lead clip on the back and front for using with a lead on both, and vecro pocket for id tags and is fully adjustable.