Assuming crypt wendtii isn't doing it for you?
There are some options, but they will require trimming to stay small...
Sunset hygro (dosing iron will bring out red color)
Nymphaea daubenyana African water lily (Absolutely awesome plant, but super hard to find. Bright red, stays short, would be perfect.)
Nymphaea pubescens is larger, but will also work.
Echinodorus' Klienar Prinz' is a small echinodorus with red young leaves.. Maxes out at 12 inches tall.
Have you tried yellow plants? If not, Golden Lloydiella (Lysimachia Nummularia var. Aurea) or Nesea 'Gold' could work. Both require trimming. There'a a golden variety of anubias nana
, but I can never find it.
Another great contrast plant is prosperinica sp... Either one works well, and will turn orange with good light.