Carbon V Brake Pad Options

[CamMancuso]

I have a set of Shimano BR550 brakes on my cross bike, but am having an issue finding carbon pads aside from the Swissstop rx yellow's that will fit the longer cartidge. I wouldn't mind having the yellows but I paid $15 for the brakeset and don't want to spend over three times what they're worth on swissstop pads. Since cross season is halfway over I don't care how long the pads will last, I just want the brakes to actually work with my race wheels and stop the squeeling. Anyone have any other options in the less than or around $20 range?