use this forum as a masterpost for tape resources. this can include anything from j-card templates to shops which sell blanks. make sure you've tried and tested before recommending ! i'll also reply with resources which i use :D
this is a uk-based site which sells colourful blanks with custom tape lengths. there are also a selection of cases so choose form (both with and without pins). while the site looks a bit dated, i've only ever ordered from there and had great experiences so they're definitely worth a look !