Aria here, I'm on the Social Care team at Shopify. ??
We do have apps in our app store with suppliers who can ship from the States. These are the main two who can provide men's accessories from the US:
You can find more suppliers in our app store, here.
I'm sure it can be a profitable niche. It's all about how you market the products and build interest in your brand. When you're deciding on a product for your store, it can be useful to consider what you're passionate about as it makes it easier to generate content that can drive traffic to your store. I personally like to do things backwards: come up with a marketing plan first and that will lead you to your product. I listened to a Podcast earlier today, I think you might find it inspiring:
I'd be interested to hear how you get on. Let me know if you need anything else. ?
Social Care Guru