What type of blue LED (power, packaging, actual colour)?
What quality do you want?
1000 LEDs (especially if they're low power LEDs) is still a small purchase.
If you're not concerned about the actual colour, quality or the matching between LEDs, and especially if you're not too concerned about their lifetime, there are a plethora of sites (
ebay,
aliexpress,
ledshoppe, and many more)
On the other hand, if you're after something That might even have a datasheet, try
mouser,
digikey,
element14,
RS)
You don't mention where you are (for all I know, you might be in Europe), so I didn't bother much about the currency. There are a lot of places.
Sorry if this wasn't much help, you were a bit light-on on details.