the dirt cheapest way i can think of is retrofit a string of small christmas light LEDS. get white ones. and some wire strippers.
(I'm really not kidding.)
He wanted RGB though, so white wouldn't work for him.
It's late, so he likely missed any of the after Christmas sales anyways, so his choice now would be to hit up eBay or DX.com
after he chooses his desired controller. The PacLED64 and LED-Wiz uses
common anode RGD LEDs, if another controller is chosen, the OP will need to do his due diligence.
Op can also hit up Digikey or Mouser for LED's but while those are guaranteed quality, they're also expensive as hell.
Don't forget the resistors if the controller needs them.
To the OP, the products by Ultimarc are good and they have excellent support. Just pick what fits your needs and go with it.
I don't actually own Ultimarc's controllers as I tend to build my own. But if I wasn't doing that, they're definitely worth considering.