Sorry can't give you any recommendations where to find the compounds in your country, but... here's the breakdown on the original 5-Stars PBW product.
Regardless of all the (7th Generation) adjuncts being added in this thread, let me reiterate: 5-Stars PBW consists of 70% Sodium Percarbonate and 30% Sodium Metasilicate, with a very small amount of Sodium EDTA added, which may be skipped for good measure.
The Sodium Percarbonate is probably around 98% pure (Tech grade), which means it isn't cut with much cheaper Sodium Carbonate (common washing soda aka soda ash). Oxiclean "(fragrance) Free" and generics are typically cut with washing soda as high as 40/60. The content should be listed on the container. But the oxygen action is much overrated IMO, so it doesn't matter if it's cut by quite a bit.
You can use TSP (TriSodium Phosphate) instead of Sodium Metasilicate. TSP was banned in some countries years ago, and Metasilicate is a suitable substitute when used as a cleaner/degreaser.