You can get a good used one at Ebay for cheap.
Your remote is not the issue. You are suffering from a botched Xiaomi firmware build.
Find and flash Oreo build 2179. Complete instructions available in this subreddit.
$12 Shipped?
u can buy for 10€ the real ones on aliexpress
Wait for the new fire stick to come out next week and see if that remote works.
I can sell mine if you'd like
Can't you just get an app on your phone to control it?
and sell me your shitty MiBox