Hydraulic Lime or lime putty where to buy?

I've long over due job to do - rebuilding the corner of an old shed wall so I can reroof the shed.

The wall is the traditional 2ft thick random stone set in lime mortar with rubble core. I've a feeling the walls are still moving a bit (house has no foundations so I guess the old sheds are the same) so I don't really want to use modern cement and make one corner immovable. Ideally I'd like to use lime mortar so the walls can move without cracking.

So I want some hydraulic lime or lime putty but where to get it around the Waterford area? I can drive to Dublin to get it but I really don't want to do that.

The easy to get White Rhino Hydrated Lime isn't the same as Hydraulic Lime and doesn't set so isn't any good.

I'll probably end up using a weak cement mix but I'm at least going to investigate using lime mortar first.