You could try local kijiji for fish or try local online FB pages for fish stock. I find sometimes you get good deals!
I also sell fish on those sites, they are good sites for people who are not running a business but need to offload extra fish or re-home unwanted fish.
also, may I suggest a larger tank? A 10 or even 20g tank would be easier to maintain...I hate my small 4g and 5g tanks they are the most difficult to maintain and I hate doing the maintenance on those two tanks more so than my 60 and 135g