Hi, there is currently a semiconductor shortage!
I wanted to purchase about 200 pieces, but I was unable to do so. 6wks wait time.
Maybe they are available elsewhere, but they will be expensive.
@Onizuka18
When you purchased the K5100M it was supplied with a 
1Mbit chip size (PMC Pm25LD010 2.7-3.6V 1024Kx1S)
This is not necessarily a mistake. If the vendor uses this card in a PC laptop without uefi, then the ROM will fit no problem. They don't know that you are intending to use this on a mac.
For our purposes, we always used a minimum of 
2Mbit chip size (PMC 
Pm25LD020)
other alternatives are:
Winbond 
25x20CLNIG
Macronix 
MX25L2006EM1I-12G
You can reference this post 
<EEPROM Replacement>
For external flashing <
<CH341a>