I Suggest to use https://www.banggood.com, You can find many varieties of Stationery Items. Check here https://www.banggood.com/search/stationery.html
The shipping times are good, with free shipping you will get item in 7-20 days, even with paid shipping(shipping costs from $1 to $2 USD)
will get you item with 7-12 days,
As an example, you can check this item https://www.banggood.com/6-Pcs-Candy-Color-Plastic-Ink-Gel-Pen-Set-Highlighter-Office-School-Station...
Also check the attached screenshot(shipping.jpg) of shipping times.
You can easily import items from banggood.com using our app at https://apps.shopify.com/dsmatepro
My name is Jade, I am with the Support Team at Shopify! You may be interested in checking out the app Kite for your store because they do some stationary products. Kit is a print-on-demand app that allows you to design your own products. Here is a link to their stationary and other product listings.
Have a wonderful day \ (•◡•) /
You can start your search for the right partner on: Amazon, eBay, Banggood, Chinavasion or Walmart and so on. And you can import products from Amazon, eBay, Banggood & Walmart to your Shopify store via ShopMaster(shopmaster.com).