Id call local tyre places.
I once got a part worn tyre from a place I thought only did new tyres. They only charged me £20 notes and it was canny good tbh.
I know a place that does them. I went into save on (BK), but when i went in i was told their part worns are limited and ordered by customers in advance. There are plenty of places selling Part worns around the country, it just seems their tight down here.
I had a better idea though, get some wheels, wheels/tyres used is like the same price as getting 4 new tyres, and ive called a shop who has a set with 6mm of tread on, lol 6mm will last me like 2 years
, plus ill be getting 16s instead of 15s, or if i can find some 17s maybe, but my preference is to stick to OEM wheels.