The parts are available at compassmicro.com (in north america)
There are essentially two printer parts that can cause this issue (aside from just a bad head): the cleaning assembly (vacuum and flush pad etc) and ink supply assembly (ink lines, dampers, and inlet spikes that the cartridges go into).
BUT, The first thing to do is buy an OEM (Epson) Magenta cartridge and put it in. Do some cleanings and see if anything changes. This is the cheapest and easiest solution to see if something is just stuck at the cartridge end. If that clears it up we'll send you a new cartridge.
If it doesn't clear up, the next solution is really up to you. It can be more expensive in time to replace the ink and cleaning assembly and it is not guaranteed to solve the problem if the head has been damaged by the printer being in this state.