7x9, 7x10 trauma plates?

I have a second chance carrier with an odd max size. Measured a test piece of cardboard and absolute max I can go is 7.5” wide by 10” tall. There’s no other markings besides the brand so I don’t know intended plates were supposed to go in it. It has a t-15 plate currently in it, looking to upgrade since it only stops 9mil +p and 12ga slugs. Any recommendations on level III+ or IV plates for the carrier?