Philadelphia is not the best choice, if you are eating clean, as it has thickeners. Sainsbury’s SO organic soft cheese has no additives, 24.5g fat per 100g and 3.1g carbs per 100g. Currently (03/08/20 or 08/03/20) Sainsbury’s price is 1.55 for 250g.
For those eating clean, organic sour cream would be better, as made with organic single cream. If you don’t have any. or wish to experiment, you could try making this recipe with creme fraiche, which is cultured double cream. The best creme fraiche comes from Normandy. Something like D’Isigny creme fraiche will be around 40% fat.