Take measurements to see exactly how much space you can spare, then search "acrylic risers display" on Amazon. You can add "cards" or other keywords to narrow. "Single" might be good because a lot of them are multi-tiered.

Find listings comparable to this one here and compare your depth and height requirements against the specs to make sure they'll fit, and you should be gravy.

Looking sweet btw, will be even cooler with a back row and maybe something framed above or a couple pennants if you're an old fuck like me and they even still make pennants 😅