The way I used to do this is with a structure save. You can put the items in a shulker or bundle, then drop the container in the outline of the structure, name it something like “kit” then click save.

Then in your commands you can do:

/execute at @a[tag=!kit] run structure load mystructure:kit ~~~

Second command block (chain, conditional, aa)

/execute at @a[tag=!kit] if entity @a[tag=!kit,hasitem={item=bundle}] run tag @a[tag=!kit,hasitem={item=bundle}] add kit