Short answer — the Malaysian apps where people commonly list Cartier pieces, “Cartier‑style” / “Cartier‑inspired” (and also pre‑owned or look‑alikes) are:

• Shopee (Shopee Malaysia) — large marketplace where sellers list fashion watches and “for Cartier / Tank‑style” items. (compare.iprice.my)
• Lazada (Lazada Malaysia) — similar marketplace listings and accessories marketed “for Cartier/Tank”. (lazada.com.my)
• Carousell Malaysia — lots of pre‑owned authentic Cartier and private sellers advertising lookalikes; good for second‑hand pieces. (carousell.com.my)
• Mudah.my — Malaysian classifieds with pre‑owned Cartier watches and private listings. (mudah.my)
• Zalora — fashion retailer app that stocks dress/watch brands that make Tank‑style or rectangular dress watches (more likely legal “inspired” designs from fashion brands). (zalora.com.my)
• Chrono24 / authorized sellers — if you want genuine Cartier (new or pre‑owned) rather than lookalikes, use official Cartier channels or reputable marketplaces that specialise in luxury watches. (cartier.com)

A couple of notes:

• Many cheap “Cartier‑style” items on mass marketplaces may be unofficial homages or counterfeit/replica products. Replica sellers do operate in Malaysia (examples appear on local sites), but buying counterfeits has legal, quality and warranty risks — I don’t recommend it. (csfactorywatch.com)
• If you want a lawful look similar to Taylor Swift’s (Cartier Tank / Panthère styles), search those marketplaces for terms like “Tank‑style rectangular watch”, “Panthère inspired bracelet watch”, or look for reputable brands that make rectangular dress watches (and always check seller ratings, return policy and authenticity paperwork).

If you want, I can search one of these apps now for currently available listings that match the exact style you mean (e.g., Tank or Panthère look) and show a few options.