If you're using Craft Pro, the included Product Details Field Type can be queried with Craft's native GraphQL. Use your Field Type handle and specify whichever product details you need:
myFieldHandle {
sku
price
shippable
taxable
weight
weightUnit
length
width
height
inventory
dimensionsUnit
}
Example JSON result:
"myFieldHandle": {
"sku": "infinity-gauntlet",
"price": 499.98,
"shippable": true,
"taxable": false,
"weight": 1360.776,
"weightUnit": "grams",
"length": 36,
"width": 21,
"height": 21,
"inventory": null,
"dimensionsUnit": "inches"
}