Short answer — Taylor Swift wore brown Louis Vuitton heeled sandals for her engagement look (often identified as the LV Isola/Isola-style sandal). To buy the same or very similar pairs, try:

• Louis Vuitton boutiques or the official LouisVuitton.com site — the LV Isola sandal is listed on the brand’s U.S. site (buy new, guaranteed authentic and current stock). (us.louisvuitton.com)
• Major luxury department stores and authorized retailers that stock Louis Vuitton shoes (Saks Fifth Avenue, Neiman Marcus, Bergdorf Goodman) — good if you want in-person try-on or store pickup. (If you want, I can check current stock at a specific store.)
• Online luxury multi-brand retailers (Net‑A‑Porter, Farfetch, Mytheresa, MATCHESFASHION) — useful if a particular size or color is sold out at LV’s site.
• Pre-owned / consignment marketplaces if the exact color/season is sold out or discontinued: The RealReal and Vestiaire Collective both list Louis Vuitton sandals (including LV Isola variants) and authenticate items before sale. (therealreal.com)

Sources confirming Swift’s engagement shoes were Louis Vuitton (brown heeled sandals / LV Isola style): Vogue and Fashionista. (vogue.com)

Quick tips when shopping

• If you buy new, use Louis Vuitton’s site or an authorized retailer for returns and sizing help. (us.louisvuitton.com)
• For pre-owned, buy from platforms that offer authentication (The RealReal, Vestiaire) and check seller ratings. (therealreal.com)
• If you want an exact match (color/season), the LV boutique or concierge can tell you whether that color is still produced or suggest the closest current style.

If you want, I can: check current stock/price at Louis Vuitton U.S. site or a specific retailer, or find close matches under $X — tell me which and I’ll look it up.