Seat Riser ?

[Blind Bobber]

My Alaskan SS has the tiller operator seat mounted on an open sided box with the fuel tank inside. I would like to find or make a quick raise (and lower) seat post. I only want seat to raise perhaps 6 inch but want it to be a quick trip. None of the risers I have seen are for box mounting. Any suggestions? I'm a low budget kinda guy. Thanks much.
BLIND BOBBER

[Splash]

Sorry, wish I could help. The only seat riser I'm familiar with is a foot rapidly approaching from my blind side.