4x4x4 led cube using mm5451 chips .. need a suggestion on a Mofet or equivalent
You apparently have the low drive for columns figured out, and are asking about the high side drive for the rows.  I don't know what a MM5451 is, but it apparently provides some kind of open drain/collector output.

Why do you think you need to control the row drivers from this MM5451 thing?  Why not control them directly from the microcontroller producing the mux signals?  In that case, PNP transistors might be easier since it's hard to find good P channel FETs that don't need much gate drive voltage.  If you can find something equivalent to a "logic level" FET in P channel, then you can drive its gate directly from the micro.  However, it only takes a single resistor to do it with a PNP transistor, and those are definitely easily available and cheap.

How much current does this high side switch need to handle?

Added:

Now that Russell has provided a link to the datasheet (now why couldn't you do that yourself in the first place?), it is clear this is not just a low side driver chip but also a serial to parallel converter which allows for a few control lines to drive lots of output lines.

Given that, it does make sense to also drive the rows from such a device.  Fortunately that is easy.  All it takes would be a P FET and a single resistor or a PNP bipolar transistor and two resistors.  The FET solution is one less part but the bipolar solution will be considerably cheaper.  Russell has already given you pointers to some suitable FETs.  Just about any jellybean PNP will be suitable.  I generally use MMBT4403 for such jellybean applications, but many other will do too.  Look up prices and you will see these are about a order of magnitude less than what Russell showed for the FETs.

To use a PNP for this, tie the emitter to the positive supply and the collector drives the LED anodes just like the drain of a P FET would.  Put a resistor between the base and the MM5451 output.  Size the resistor for about 1-2 mA base current.  Then add a second resistor between the base and the emitter (base and positive supply).  The purpose of this resistor is to make sure the transistor is off when the MM5451 is not driving.  Without this resistor, the base would float and the transistor could come on a little if it picked up sufficient noise.  10 k&Omega; is a reasonable value for this resistor.  It is high enough to only rob about 75 &micro;A from the base current, but low enough to keep the transistor solidly off when the MM5451 output is not driving low.  This PNP drive would be my first choice unless board space is a critical issue.