I got these rhinestones on eBay for $0.99 (USD) with free postage from the seller virtualvilliage-au1.
I got 1600 rhinestones so that should last me forever! They are 2mm in size which I think is a good size for my nails. One of my favourite vloggers soguesswhat11 has a video showing how to apply rhinestones.
When these arrived they were a bit mixed up because the top was ajar. I spent one night separating the colours while watching nail vlogs. Yeah I know, how could I be bothered? I don't know, I like tedious tasks.