command-blocks

(On a server with scoretp installed, summon a villager with no AI named Robot, then put these commands in a command block chain and activate it. This will make Robot mirror your X coordinate.)

(Summon the villager with a command like this)

/summon villager ~ ~ ~ {CustomName:"\"Robot\"",CustomNameVisible:1,NoAI:1}

(Command blocks:)

execute store result score @e[name=Robot] tpX run data get block ~ ~ ~ x
execute store result score @p tpX run data get entity @p Pos[0]
scoreboard players operation @e[name=Robot] tpX -= @p tpX
execute store result score Vars tpX run data get block ~ ~ ~ x
scoreboard players operation @e[name=Robot] tpX += Vars tpX
execute store result score @e[name=Robot] tpY run data get entity @e[name=Robot,limit=1] Pos[1]
execute store result score @e[name=Robot] tpZ run data get entity @e[name=Robot,limit=1] Pos[2]
execute as @e[name=Robot,limit=1] run function scoretp:tp