You won't find the P4P800 anywhere new, only refurbished or used. You didn't specify form factor, so here are some options:
BIOSTAR P4M80-M4 VIA P4M800 Prescott and Northwood up to 3.2GHz, Celeron D up to 3.06GHz, only supports
single channel memory contrary to Newegg's description (Biostar USA has a later BIOS update than Biostar Taiwan)
ASRock P4VM890 VIA P4M890 Prescott and Northwood up to 3.4GHz, Celeron D up to 3.2GHz, PCI Express x16,
single channel memory
ASRock P4i65G Intel 865G Prescott and Northwood up to 3.4GHz, Celeron D up to 3.2GHz, supports dual channel memory
ASUS P4V800D-X VIA PT880 Ultra Prescott and Nortwood up to 3.4GHz, Celeron D up to 3.2GHz, supports dual channel memory, AGP 8x and PCI Express 16x (4x operation)
ECS P4M800PRO-M478 VIA P4M800 PRO Prescott and Northwood up to 3.4GHz, Celeron D up to 3.2GHz,
single channel memory
Here's a
Gateway OEM version of the
Intel D865GLC based on Intel 865G. All versions of this board support Northwood 533MHz and 800MHz up to 3.4GHz (as well as Willamette), but only later AA revisions support Prescott and Celeron D.
I've worked on a few Gateway machines that use the Midway or Midway 2 boards. The latest Intel BIOS for D865GLC will work on this board and is much newer than the latest from Gateway. You can't update the BIOS conventionally because the board won't recognize the Intel BIOS. You have to download the recovery BIOS file from Intel and use the BIOS Configuration jumper to force the BIOS to update, but it works. Here's how:
Download the P25 BIOS recovery file from Intel and copy it to a formatted floppy disk. With the motherboard powered off, insert the disk then jumper the board for recovery mode. The floppy need not be bootable, just formatted and contain the BIOS ROM file.
Power on the computer and the watch the floppy access LED for activity. After about one full minute, the system beeps and shuts down. Remove the floppy, restore the BIOS Configuration jumper to Normal Operation position, then power the system on. Enter BIOS Setup and load defaults, then modify the BIOS options to preference. Presto chango.