api - Shopify Product Replacement Parts -

looking advice on interesting situation using shopify. i'm building site client has products have free replacement parts available. each replacement part has variant color options.

so far have had users @ company add replacement parts products in store. have filtered search results , catalog results replacment parts not show.

the place want replacement parts show when user visits product, can click button says order replacement parts. screen show replacement parts product.

a single replacement part may belong several products , may have different color variants.

so have done far had client tag parts @ least 2 tags. tag called "part" identifies product part. , 1 or more tags "link:sku123" links part 1 or more products. on product page using liquid loop parts , display ones matched products sku. found out loop has 50 item limit...

so looked @ product api, ok, except has no way filter tags. tags seem handy , yet don't see many ways use them... i'm looking way display replacement parts particular product. doesn't have involve tags, although client has tagged parts , hate tell them waste of time. thoughts on how accomplish appreciated.

the way can think it, return of replacement parts , filter through them on page. see api limited 250 products, suppose make multiple calls until them all. i'm not sure how many replacment parts there total, suspect there upwards of 1000. seems waste of network resources have pull them down , filter through them...

p.s. - replacement parts free, can run through checkout 0 dollar amount?

i create parts standalone products. each part have variants (colours). create metafields parts (product) have field list of product ids 'mother' parts. way don't need have strange tags , keep concepts more separated, & cleaner. per 0 amount, yes, can go checkout 0 amount (if shipping settings allow so).