I would go with Amazon unless you want to get a custom frame made or use a larger frame with a mat. Standard USA size would be 6 x 8.

6x8 finished for a 4x6 image, yes?

How about Wayfair? (I try when possible to avoid Amazon.)

6x9 used to be the size photo that the photo shops printed ... so they always had a wide range of frames. It is not a full frame photo image (they start at 5x8) but it was very a very common size frame 10-15 yr ago.

Interesting Funky, thx.

Eld, I don't like Wayfair's return policy.

It sounds like you can get this off the shelf, so this is just a general FYI. When I have something that's an odd size but I don't want to spring for custom framing, I've used Frame Destination. Not a huge selection, but they'll cut the frame/glass/matt to any size you want. Pricing is more than off-the-shelf but significantly less than a custom frame shop.

Mtn, interesting. I only had to return one thing and replace another. I’ve been happy with all my purchases, but will look closer to that next time I order.

Try Etsy? I got a frame that size there, but it was wood.

I have also found odd sizes at a local art supply store.

Try this from Dick Blick if you want a very minimalist frame

https://www.dickblick.com/products/swiss-poster-clip-hangers-kit/

While you are there, look around at the other Dick Blick frame offerings. I scanned it quickly, but I was confused about the size you were needing. I have bought from Dick Blick when I have small, standard size pictures. I’ve used both their floating frames and their plein air frames. Their customer service is top notch and can give you all sorts of options if you call them.

You can float them in a slightly bigger frame. Seeing the edges might be nice.

Very nice! Love that narrow brass and it is especially appropriate for any artifact from India. I have floated something that was a non-standard size in a larger frame and it looked pretty good.