If assembling the frame yourself is an option, I would recommend American Frame. A nice matte black frame will run you about $25:

https://www.americanframe.com/frames/matte-black-metal-picture-frame-r21.aspx

American Frame automatically adds the acrylic, backing board and Mat board to your cart when you choose the dimensions, but you simply remove those as they won't be needed. Add a note to your order to send a couple of sawtooth hangers instead of the overly complex wire/loop hangers and you are good to go.

Once you receive the kit, just add some felt to the ends of four of the tensioners and put one tensioner on each side of the glass to hold the backglass in the frame.