If you want community add Charax to the list above (if you can find them)
If you're open to future tank upgrades a small shoal of Dorado would be all you need. When available, if you get them small, they can be very reasonably priced. Twice the energy/activity level of most fish. Probobly not gonna be real friendly to any of the above tankmates.
Shoal of Brycon. Would fit tank and price requirements, but tank mates might not be an option.