Assuming this is 5g, you can certainly put 6-8 chili rasboras in there. Other options include other rasboras species such as
Boraras urophthalmoides
Boraras maculatus
boraras merah
Or even Ember Tetras or some dwarf cories (habrosus, pygmaeus, or hastatus).
Rachel has some of these in stock, now.
http://msjinkzd.com/stocklist/
As I said earlier, none of these species would be happy although they would survive in the tank.
And I would strongly recommend against B. Uropthamoides which naturally congregates in schools of 1000's and B.Maculatus which requires stream like habitats and ample swimming room.
I did a bit of digging to find a more suitable fish since Bettas aren't too your liking, and the only other thing I can in good conscience recommend are Danionella species and micro crabs.
Other than Killifish and Betta, there's not really much readily on the market which would be ideal.
I do believe that Rachel O'Leary carries Danionella too, if you wanted to go that route.
She's a very good seller and could offer you some great advice.
Bump: Nice tank you got there though man! I'm sure something would be happy in there
The other thing I forgot to mention is that B. Merah is extremely similar to B. Brigittae, so there's not much difference there in terms of care and requirements.
I still wouldn't have them in a 5 gallon though.
Why not stick with shrimp? They're beautiful and very interesting. And there are a great variety of different types if you want to get into it
