I’d contact RedStag Fulfillment for large SKU counts, SKUs with variants (like the jewelry sizing you mentioned above) and high-value merchandise fulfillment. They have a very secure storage and fulfillment process that video-tracks every step of the fulfillment process for high-value merchandise, plus they tend to handle higher SKU counts for products with variants. They may be just what you’re looking for. Here are user reviews and a quick-contact form for RedStag Fulfillment.
Hope this helps!