I think the c't magazine in Germany once had a kit to build an ISA or PCI card to program stuff. But frankly, I'd look into a seperate bulk eraser and an external eprom programming unit. I think they are around in the second-hand area.
there is no way to program a cmos eprom on a pci card either. the only exception: the pci card is a special multi-purpose-programming card (very very expensive and for hardware developers only).
look here. if you're skilled you can build your own.
the ct' flasher supports (like the name already suggests) writing to flash eproms only. uniflash supports the ct'flasher just in case someone wants to know how to avoid the original ct'flasher software.
like i stated in my previous post in this topic there is a difference between eprom, eeprom and flash-eeprom.
eeprom and flash-eeprom are almost identical. they just differ in programming speed as they use different techniques of writing the data into the chip. both can be electrically erased.
eprom need uv-light to be erased, use different programming algorithms and are way slower in programming speed.
reading them all is somewhat the same: set address, enable output, get data from output, disable output, set address, enable output, get data from output, disable output, ...
so if you are smart, you can program a (flash-)eeprom in your mainboard and build an adaptor to your nic bootrom socket (which are build to be fitted with eproms).
this should help you for a start. if those nics are eprom equipable you should buy a programmer (maybe a readymade version), an uv-eraser and lots of eproms ;)
there are cards available (most intel equipped cards) which already have an flash eeprom chip onboard (yes, eeprom..reprogrammable) to support etherboot. so with those cards you won't have to mess around with an eprom burner. but be aware that those cards are more expensive than the $1 budget cards you can buy everywhere.
even the budget cards have PXE support but they need an additional (e)eprom..some (more expensive) cards already have an eeprom soldered on the nic. there were lots of dell/compaq/hp nics on a huge internet auction platform lately. they were equipped with intel SB82558B (10/100Mbit) and had a 512kbit eeprom soldered on the board. they were a real bargain.