Besides the obvious option of looking on eBay, here are the proxy services and merchant sites I have used as a Canadian for services that don’t offer international shipping.
I recommend checking these regularly, because many of these items are quite rare and will not go up for sale very often.
Make an account on https://dejapan.com. They have a built-in search engine that will search multiple merchant sites for you (Yahoo Japan Auctions, Rakuten, Fril/Rakuma, Suruga-ya, Yahoo Shopping, and Mercari). Search for “スーパーマリオRPG” and order directly from Dejapan’s search results.
There are lots of options for Japanese proxy services other than Dejapan, but I specifically recommend them as it’d be putting it lightly to say that their customer service is top-notch.
Make an account on https://www.delivered.co.kr/. Search https://globalbunjang.com/ for "마리오 RPG”. Global Bunjang is integrated with Delivered Korea, so you can click “Buy” directly on the Global Bunjang item listing and it will prompt you to use your Delivered Korea account. You can also try searching on auctions.co.kr, or try your luck with the possibly-outdated listings on https://bbs.ruliweb.com/market/board/1020/read/78782.
Search https://shopee.tw/ for "超級瑪利歐 RPG”. If you find an item listing you like, fill out this form on Buy Taiwan Online and they will get back to you with payment info: https://buytaiwanonline.com/pages/request
Search https://buygame2.com for “超級瑪利歐 RPG”. No need to use a proxy service for this one, they deliver internationally.
(Note: The parcel was not tracked after it reached Canada.)
This only applies for the metal pin set, which I could never find on eBay. Nintendo’s UK store only delivers within the UK, so make an account on https://www.myukmailbox.com/. Order directly from https://store.nintendo.co.uk/en/super-mario-rpg-pin-set-bundle-B00476 but put your My UK Mailbox account address as the shipping address. Do this soon because the pin set won’t be there forever!
(note: the pin set is not sold separately, it requires a purchase of the game)
Unfortunately I don’t know of a reliable way to get the sticker set overseas. The retailer only ships domestically, and I don’t know of any Chilean proxy services.