I didn't pick up a Neo-Geo Mini but I did pick up a controller since they're USB. It actually has a nice weight to it but the clicky stick is gone (expected)
NEO-GEO-daptor - NEO-GEO AES to USB interface
NEOGEO miniでも使える!主要ハードほぼ全ての8機種対応アーケードスティック「Mayflash F300」を試してみた 【使って試してみました! ゲームグッズ研究所】 - GAME Watch
raphnet. - Neo Geo controller to USB adapter
NEOGEO Arcade Stick Pro | SNK
raphnet. - Neo Geo controller to USB adapter
Building a Neo Geo Stick USB Adapter : 7 Steps (with Pictures) - Instructables
Neo Geo X USB Controller - Lakka - Libretro Forums
Modded NEO GEO X controller complete! (PC/AES/NGCD compatible) : r/neogeo
Neo-Geo CD Controller [Japan Import] : Video Games - Amazon.com
Amazon.com: NEOGEO mini PAD(Black) : Video Games
NEO GEO Stick Joy Controller for Original Geo Neo AES oOperation test STERILIZED | eBay
SNK releases Neo Geo pad for PS3 | Engadget
Hardware: NEO-GEO PlayStation 3 Gamepad (Import) Review - YouTube
Neo-Geo Arcade Stick Original, Video Gaming, Gaming Accessories, Controllers on Carousell
PlayStation 2 NEO-GEO Neo Geo Pad 2 Controller - (PS2) PlayStation 2 [ – J&L Video Games New York City