Ultra Pro Top Loaders are the best quality but are around $10-12 for 25. They also sell boxes that’ll hold around 60-70 cards in the sleeves so that’s what I do.

Ultra Pro 3" x 4" Super Clear Premium Toploader Card Protector | 25-Count per Pack | 2-Packs https://www.amazon.com/dp/B07CG4VDNS/ref=cm_sw_r_cp_api_glt_fabc_CD6V3B51MAYRD0Z0YC9Q