Several things. One, creating a plugin is programming work and depending on how complex the project, may require specialized knowledge. Two, you’re essentially asking for volunteer work on top of the work requiring special expertise. Small ideas or ideas that can be done with freely available plugins, you can easily find a nice person swing by a forum post and give you help for free. However if you really mean that you’re doing a “unique” skin system and that no publically-available plugin can do what you want, you’re going to hit a dead end fast.
Three, if you’re willing to pay, there’s this guy: [OPEN] Nat’s RMMV & RMMZ Plugin Commissions - RPG Maker / Chat - RPG MAKER GUILD
Four, if you literally are just asking how to request a plugin, I think posting in this forum is okay? (not a moderator)