How about the Bundles app of Shopify itself? https://apps.shopify.com/shopify-bundles
If I understand it well, with that app you can have 1 SKU in your inventory and create multiple bundles (where you add 1 product) and give all the same SKU + barcode. Then multiple products in your front end will be supplied by 1 SKU, with 1 barcode and one product in your backend (Shopify inventory).