Recently viewed widget – “out of stock”

Hi – I thought this would be relatively easy, I just need to change where it says “Out of stock” to “Sold out” in the Recently Viewed widget. I have tried adding to themefolderi18nen_GB.csv

"Out of stock","Sold out" 

and also to themefolderMagento_Catalogi18nen_GB.csv but neither works. This is how it appears in the browser

<div class="stock unavailable">

<span data-bind="i18n: 'Out of stock'">Out of stock</span>

</div>

I was going to just change it in the relevant phtml file but can’t find the correct one. Can anyone pointme to the actual HTML for the items in this widget? Thanks