Depending what the item is if there is the same shop in T3 contact them in advance and they should be able to have it brought over as long as it is if high enough value to make it worth their while.

if you do do the escorted service make sure you have plenty of time and remember you will have to go through security at both T5 when you get there and T3 when you return.

If yiu were thinking of trying to enter T5 from landslide that won’t work as you need a T5 BP