Skandix list an aftermarket cat at 370 euros plus shipping and import tax, which can be considerable. You may be able to purchase cheaper in UK, but avoid a cheap one as they can be inefficient. My previous V40 cooked its cat and I fitted a cheap replacement, next mot the tester had to rev the engine at full throttle and get the block white hot to pass. I think he also boiled the oil!. I vowed there and then that I would change it before the next mot. Fitted a secondhand genuine cat and next mot it sailed through without any issues. Tester said, 'A bit different to last year'!.
Buy comparison the Mini cat was £1200 exchange from Mini with a good discount.
Just checked Parts for Volvo Online
https://www.partsforvolvosonline.com...d46c3fc08b9e8a
They are a reputable company and although I haven't got any direct experience of their cat's I have dealt with them for many years and always good quality at reasonable prices.