Would it be possible to keep a Betta (Siamese Fighting Fish)
if you do keep a betta, your options will be pretty limited in terms of tankmates. colorful fish generally wont work with bettas but there are some options that are still interesting.
5 or 6 glass catfish would work, they arent colorful but theyre definitely an eyecatcher because you can see right through em

unlike most catfish, they swim mainly in the mid to top levels of the tank.
someone else mentioned rasboras. im not 100% on that but i'll take their word for it
corydoras or ghost shrimp would work too, but i dont know how 'attractive' they are.
african dwarf frogs work too.
all of these fish are commonly available so finding them in a pet store shouldnt be a challenge. good luck.